summaryrefslogtreecommitdiffstats
path: root/2023/captions/emacsconf-2023-gc--emacsgcstats-does-garbage-collection-actually-slow-down-emacs--ihor-radchenko--main.vtt
diff options
context:
space:
mode:
Diffstat (limited to '')
-rw-r--r--2023/captions/emacsconf-2023-gc--emacsgcstats-does-garbage-collection-actually-slow-down-emacs--ihor-radchenko--main.vtt1780
1 files changed, 1780 insertions, 0 deletions
diff --git a/2023/captions/emacsconf-2023-gc--emacsgcstats-does-garbage-collection-actually-slow-down-emacs--ihor-radchenko--main.vtt b/2023/captions/emacsconf-2023-gc--emacsgcstats-does-garbage-collection-actually-slow-down-emacs--ihor-radchenko--main.vtt
new file mode 100644
index 00000000..d1e2a5f6
--- /dev/null
+++ b/2023/captions/emacsconf-2023-gc--emacsgcstats-does-garbage-collection-actually-slow-down-emacs--ihor-radchenko--main.vtt
@@ -0,0 +1,1780 @@
+WEBVTT captioned by sachac
+
+NOTE Introduction
+
+00:00:00.000 --> 00:00:04.639
+Hello everyone, my name is Ihor Radchenko,
+
+00:00:04.640 --> 00:00:07.599
+and you may know me from Org Mailing List.
+
+00:00:07.600 --> 00:00:09.799
+However, today I'm not going to talk about Org Mode.
+
+00:00:09.800 --> 00:00:11.919
+Today I'm going to talk about
+
+00:00:11.920 --> 00:00:14.959
+Emacs performance and how it's affected
+
+00:00:14.960 --> 00:00:19.039
+by its memory management code.
+
+00:00:19.040 --> 00:00:21.639
+First, I will introduce the basic concepts
+
+00:00:21.640 --> 00:00:26.439
+of Emacs memory management and what garbage collection is.
+
+00:00:26.440 --> 00:00:30.559
+Then I will show you user statistics
+
+00:00:30.560 --> 00:00:34.959
+collected from volunteer users over the last half year
+
+00:00:34.960 --> 00:00:39.319
+and I will end with some guidelines
+
+00:00:39.320 --> 00:00:44.719
+on how to tweak Emacs garbage collection customizations
+
+00:00:44.720 --> 00:00:47.479
+to optimize Emacs performance
+
+00:00:47.480 --> 00:00:51.079
+and when it's necessary or not to do.
+
+NOTE About garbage collection in Emacs
+
+00:00:51.080 --> 00:00:54.519
+Let's begin. What is garbage collection?
+
+00:00:54.520 --> 00:00:56.519
+To understand what is garbage collection,
+
+00:00:56.520 --> 00:00:59.039
+we need to realize that anything you do in Emacs
+
+00:00:59.040 --> 00:01:02.119
+is some kind of command. Any command is most likely
+
+00:01:02.120 --> 00:01:05.839
+running some Elisp code. Every time you run Elisp code,
+
+00:01:05.840 --> 00:01:09.239
+you most likely need to locate certain memory in RAM.
+
+00:01:09.240 --> 00:01:12.879
+Some of this memory is retained for a long time
+
+00:01:12.880 --> 00:01:15.559
+and some of this memory is transient.
+
+00:01:15.560 --> 00:01:19.119
+Of course, Emacs has to clear this transient memory
+
+00:01:19.120 --> 00:01:21.439
+from time to time, to not occupy all the possible RAM
+
+00:01:21.440 --> 00:01:21.447
+in the computer. In this small example,
+
+00:01:21.448 --> 00:01:28.639
+we have one global variable
+
+00:01:28.640 --> 00:01:31.279
+that is assigned a value,
+
+00:01:31.280 --> 00:01:33.079
+but when assigning the value,
+
+00:01:33.080 --> 00:01:35.679
+we first allocate a temporary variable
+
+00:01:35.680 --> 00:01:37.119
+and then a temporary list
+
+00:01:37.120 --> 00:01:40.079
+and only retain some part of this list
+
+00:01:40.080 --> 00:01:42.079
+in this global variable.
+
+00:01:42.080 --> 00:01:44.799
+In terms of memory graph
+
+00:01:44.800 --> 00:01:50.359
+we can represent this as two variable slots,
+
+00:01:50.360 --> 00:01:53.159
+one transient, one permanent,
+
+00:01:53.160 --> 00:01:56.199
+and then a list of three cons cells,
+
+00:01:56.200 --> 00:02:01.959
+part of which is retained as a global variable
+
+00:02:01.960 --> 00:02:04.999
+but part of it which is a temporary variable symbol.
+
+00:02:05.000 --> 00:02:07.679
+The first term of the list is not used
+
+00:02:07.680 --> 00:02:09.759
+and it might be cleared at some point.
+
+NOTE Garbage collection in Emacs
+
+00:02:09.760 --> 00:02:12.239
+So that's what Emacs does.
+
+00:02:12.240 --> 00:02:15.919
+Every now and then, Emacs goes through all the memory
+
+00:02:15.920 --> 00:02:19.119
+and identifies which part of the memory are not used
+
+00:02:19.120 --> 00:02:23.759
+and then clear them so that it can free up the RAM.
+
+00:02:23.760 --> 00:02:25.919
+This process is called garbage collection
+
+00:02:25.920 --> 00:02:28.919
+and Emacs uses a very simple and old algorithm
+
+00:02:28.920 --> 00:02:30.559
+which is called Mark & Sweep.
+
+00:02:30.560 --> 00:02:33.759
+So doing this mark and sweep process
+
+00:02:33.760 --> 00:02:34.879
+is basically two stages.
+
+00:02:34.880 --> 00:02:40.039
+First, Emacs scans all the memory that is allocated
+
+00:02:40.040 --> 00:02:42.759
+and then identifies which memory is still in use
+
+00:02:42.760 --> 00:02:45.519
+which is linked to some variables, for example,
+
+00:02:45.520 --> 00:02:47.599
+and which memory is not used anymore
+
+00:02:47.600 --> 00:02:49.559
+even though it was allocated in the past.
+
+00:02:49.560 --> 00:02:52.999
+The second stage [??] whenever a memory is not,
+
+00:02:53.000 --> 00:02:59.319
+that is not allocated. During the process
+
+00:02:59.320 --> 00:03:00.759
+Emacs cannot do anything now.
+
+00:03:00.760 --> 00:03:04.159
+So basically, every time Emacs scans the memory,
+
+00:03:04.160 --> 00:03:07.199
+it freezes up and doesn't respond to anything,
+
+00:03:07.200 --> 00:03:10.959
+and if it takes too much time so that users can notice it,
+
+00:03:10.960 --> 00:03:13.399
+then of course Emacs is not responsive at all,
+
+00:03:13.400 --> 00:03:19.439
+and if this garbage collection is triggered too frequently,
+
+00:03:19.440 --> 00:03:22.399
+then it's not just not responsive every now and then.
+
+00:03:22.400 --> 00:03:24.679
+It's also not responsive all the time,
+
+00:03:24.680 --> 00:03:26.079
+almost all the time,
+
+00:03:26.080 --> 00:03:27.679
+so it cannot even normally type or stuff
+
+00:03:27.680 --> 00:03:32.439
+or do some normal commands.
+
+00:03:32.440 --> 00:03:36.719
+This mark and sweep algorithm is taking longer
+
+00:03:36.720 --> 00:03:40.199
+the more memory Emacs uses. So basically,
+
+00:03:40.200 --> 00:03:44.439
+the more buffers you open, the more packages you load,
+
+00:03:44.440 --> 00:03:48.319
+the more complex commands you run, the more memory is used,
+
+00:03:48.320 --> 00:03:52.279
+and basically, the longer Emacs takes
+
+00:03:52.280 --> 00:03:57.919
+to perform a single garbage collection.
+
+00:03:57.920 --> 00:04:02.279
+Of course, Emacs being Emacs
+
+00:04:02.280 --> 00:04:06.039
+this garbage collection can be tweaked.
+
+00:04:06.040 --> 00:04:08.279
+In particular users can tweak
+
+00:04:08.280 --> 00:04:10.639
+how frequently Emacs does garbage collection
+
+00:04:10.640 --> 00:04:13.879
+using two basic variables: `gc-cons-threshold`
+
+00:04:13.880 --> 00:04:15.519
+and `gc-cons-percentage`.
+
+00:04:15.520 --> 00:04:21.599
+`gc-cons-threshold` is the raw number of kilobytes
+
+00:04:21.600 --> 00:04:22.479
+Emacs needs to allocate
+
+00:04:22.480 --> 00:04:25.959
+before triggering another garbage collection,
+
+00:04:25.960 --> 00:04:27.799
+and the `gc-cons-percentage` is similar,
+
+00:04:27.800 --> 00:04:30.399
+but it's defined in terms of fraction
+
+00:04:30.400 --> 00:04:34.759
+of already-allocated memory.
+
+00:04:34.760 --> 00:04:38.239
+If you follow various Emacs forums,
+
+00:04:38.240 --> 00:04:41.959
+you may be familiar with people complaining about
+
+00:04:41.960 --> 00:04:46.479
+garbage collection. There are many many suggestions
+
+00:04:46.480 --> 00:04:48.039
+about what to do with it.
+
+00:04:48.040 --> 00:04:54.079
+Most frequently, you see `gc-cons-threshold`
+
+00:04:54.080 --> 00:04:56.879
+recommended to be increased,
+
+00:04:56.880 --> 00:05:01.439
+and a number of pre-packaged Emacs distributions
+
+00:05:01.440 --> 00:05:04.319
+like Doom Emacs do increase it.
+
+00:05:04.320 --> 00:05:07.279
+I have seen suggestions which are actually horrible
+
+00:05:07.280 --> 00:05:10.479
+to disable garbage collection temporarily
+
+00:05:10.480 --> 00:05:14.359
+or for a long time.
+
+00:05:14.360 --> 00:05:17.519
+Which is nice... You can see it quite frequently,
+
+00:05:17.520 --> 00:05:19.399
+which indicates there might be some problem.
+
+00:05:19.400 --> 00:05:23.959
+However, every time one user poses about this problem,
+
+00:05:23.960 --> 00:05:26.879
+it's just one data point and it doesn't mean
+
+00:05:26.880 --> 00:05:28.879
+that everyone actually suffers from it.
+
+00:05:28.880 --> 00:05:33.719
+It doesn't mean that everyone should do it.
+
+00:05:33.720 --> 00:05:35.919
+So in order to understand if this garbage collection
+
+00:05:35.920 --> 00:05:39.959
+is really a problem which is a common problem
+
+00:05:39.960 --> 00:05:44.919
+we do need some kind of statistics
+
+00:05:44.920 --> 00:05:46.919
+and only using the actual statistics
+
+00:05:46.920 --> 00:05:52.759
+we can understand if it should be recommended for everyone
+
+00:05:52.760 --> 00:05:54.999
+to tweak the defaults or like whether
+
+00:05:55.000 --> 00:05:57.159
+it should be recommended for certain users
+
+00:05:57.160 --> 00:05:59.479
+or maybe it should be asked Emacs devs
+
+00:05:59.480 --> 00:06:01.559
+to do something about the defaults.
+
+00:06:01.560 --> 00:06:07.959
+And what I did some time ago is exactly this.
+
+00:06:07.960 --> 00:06:09.959
+I tried to collect the user statistics.
+
+00:06:09.960 --> 00:06:14.519
+So I wrote a small package on Elp
+
+00:06:14.520 --> 00:06:18.159
+and some users installed this package
+
+00:06:18.160 --> 00:06:22.119
+and then reported back these statistics
+
+00:06:22.120 --> 00:06:24.279
+of the garbage collection for their particular use.
+
+00:06:24.280 --> 00:06:30.799
+By now we have obtained 129 user submissions
+
+00:06:30.800 --> 00:06:34.039
+with over 1 million GC records in there.
+
+00:06:34.040 --> 00:06:38.119
+So like some of these submissions
+
+00:06:38.120 --> 00:06:43.159
+used default GC settings without any customizations.
+
+00:06:43.160 --> 00:06:46.039
+Some used increased GC cost threshold
+
+00:06:46.040 --> 00:06:47.799
+and GC cost percentage.
+
+00:06:47.800 --> 00:06:53.319
+So using this data we can try to draw
+
+00:06:53.320 --> 00:06:56.879
+some reliable conclusions on what should be done
+
+00:06:56.880 --> 00:06:59.919
+and whether should anything be done about garbage collection
+
+00:06:59.920 --> 00:07:02.639
+on Emacs dev level or at least on user level.
+
+00:07:02.640 --> 00:07:05.639
+Of course we need to keep in mind
+
+00:07:05.640 --> 00:07:07.279
+that there's some kind of bias
+
+00:07:07.280 --> 00:07:08.999
+because it's more likely
+
+00:07:09.000 --> 00:07:11.719
+that users already have problems with GC
+
+00:07:11.720 --> 00:07:13.239
+or they think they have problems with GC
+
+00:07:13.240 --> 00:07:15.919
+will report and submit the data.
+
+00:07:15.920 --> 00:07:19.999
+But anyway having s statistics is much more useful
+
+00:07:20.000 --> 00:07:22.079
+than just having anecdotal evidences
+
+00:07:22.080 --> 00:07:25.519
+from one or other reddit posts.
+
+00:07:25.520 --> 00:07:28.759
+And just one thing I will do
+
+00:07:28.760 --> 00:07:30.879
+during the rest of my presentation
+
+00:07:30.880 --> 00:07:32.839
+is that for all the statistics
+
+00:07:32.840 --> 00:07:35.679
+I will normalize user data
+
+00:07:35.680 --> 00:07:37.879
+so that every user contributes equally.
+
+00:07:37.880 --> 00:07:40.279
+For example if one user submits like
+
+00:07:40.280 --> 00:07:43.119
+100 hours Emacs uptime statistics
+
+00:07:43.120 --> 00:07:46.279
+and other users submit one hour Emacs uptime
+
+00:07:46.280 --> 00:07:52.879
+then I will anyway make it so that they contribute equally.
+
+00:07:52.880 --> 00:07:56.359
+Let's start from one of the most obvious things
+
+00:07:56.360 --> 00:07:57.679
+we can look into is
+
+00:07:57.680 --> 00:08:00.599
+which is the time it takes for garbage collection
+
+00:08:00.600 --> 00:08:05.879
+to single garbage collection process.
+
+00:08:05.880 --> 00:08:11.839
+Here you see frequency distribution of GC duration
+
+00:08:11.840 --> 00:08:14.999
+for all the 129 users we got
+
+00:08:15.000 --> 00:08:22.279
+and you can see that most of the garbage collections
+
+00:08:22.280 --> 00:08:26.999
+are done quite quickly in less than 0.1 second
+
+00:08:27.000 --> 00:08:32.199
+and less than 0.1 second is usually just not noticeable.
+
+00:08:32.200 --> 00:08:34.519
+So even though there is garbage collection
+
+00:08:34.520 --> 00:08:39.639
+it will not interrupt the work in Emacs.
+
+00:08:39.640 --> 00:08:43.279
+However there is a fraction of users
+
+00:08:43.280 --> 00:08:45.279
+who experience garbage collection
+
+00:08:45.280 --> 00:08:48.399
+it takes like 0.2, 0.3 or even half a second
+
+00:08:48.400 --> 00:08:50.399
+which will be quite noticeable.
+
+00:08:50.400 --> 00:08:55.279
+For the purposes of this study
+
+00:08:55.280 --> 00:08:59.399
+I will consider that anything that is less than 0.1 second
+
+00:08:59.400 --> 00:09:02.639
+which is insignificant so like you will not notice it
+
+00:09:02.640 --> 00:09:04.159
+and it's like obviously
+
+00:09:04.160 --> 00:09:07.479
+all the Emacs usage will be just normal.
+
+00:09:07.480 --> 00:09:11.639
+But if it's more than 0.1 or 0.2 seconds
+
+00:09:11.640 --> 00:09:13.799
+then it will be very noticeable
+
+00:09:13.800 --> 00:09:16.079
+and you will see that Emacs hang for a little while
+
+00:09:16.080 --> 00:09:21.319
+or not so little while. In terms of numbers
+
+00:09:21.320 --> 00:09:26.239
+it's better to plot the statistics not as a distribution
+
+00:09:26.240 --> 00:09:28.199
+but as a cumulative distribution.
+
+00:09:28.200 --> 00:09:31.559
+So like at every point of this graph
+
+00:09:31.560 --> 00:09:37.159
+you'll see like for example here 0.4 seconds
+
+00:09:37.160 --> 00:09:42.279
+you have this percent of like almost 90% of users
+
+00:09:42.280 --> 00:09:49.279
+have no more than 0.4 gc duration.
+
+00:09:49.280 --> 00:09:53.239
+So like we can look here if we take one
+
+00:09:53.240 --> 00:09:56.879
+gc critical gc duration which is 0.1 second
+
+00:09:56.880 --> 00:10:00.279
+0.1 second and look at how many users have
+
+00:10:00.280 --> 00:10:02.439
+it so we have 56% which is like
+
+00:10:02.440 --> 00:10:09.439
+44% users have less than 0.1 second gc duration
+
+00:10:09.440 --> 00:10:12.839
+and the rest 56% have more than 0.1 second.
+
+00:10:12.840 --> 00:10:16.279
+So you can see like more than half of users
+
+00:10:16.280 --> 00:10:20.559
+actually have noticeable gc delay
+
+00:10:20.560 --> 00:10:22.999
+so the Emacs freezes for some noticeable time
+
+00:10:23.000 --> 00:10:27.479
+and a quarter of users actually have very noticeable
+
+00:10:27.480 --> 00:10:31.799
+so like Emacs freezes such that you see an actual delay
+
+00:10:31.800 --> 00:10:36.879
+that Emacs actually has
+
+00:10:36.880 --> 00:10:44.079
+which is quite significant and important point.
+
+00:10:44.080 --> 00:10:47.719
+But apart from the duration of each individual gc
+
+00:10:47.720 --> 00:10:49.839
+it is important to see how frequent it is
+
+00:10:49.840 --> 00:10:52.879
+because even if you do notice a delay
+
+00:10:52.880 --> 00:10:54.959
+even a few seconds delay
+
+00:10:54.960 --> 00:10:56.999
+it doesn't matter if it happens once
+
+00:10:57.000 --> 00:10:59.199
+during the whole Emacs session.
+
+00:10:59.200 --> 00:11:05.039
+So if you look into frequency distribution again here
+
+00:11:05.040 --> 00:11:13.639
+I plot time between subsequent garbage collections
+
+00:11:13.640 --> 00:11:17.959
+versus how frequent it is and we have very clear trend
+
+00:11:17.960 --> 00:11:21.799
+that most of the garbage collections are quite frequent
+
+00:11:21.800 --> 00:11:25.159
+like we talk about every few seconds a few tens of seconds.
+
+00:11:25.160 --> 00:11:30.039
+There's a few outliers which are at very round numbers
+
+00:11:30.040 --> 00:11:35.839
+like 60 seconds, 120 seconds, 300 seconds.
+
+00:11:35.840 --> 00:11:37.879
+These are usually timers so like
+
+00:11:37.880 --> 00:11:40.319
+you have something running on timer
+
+00:11:40.320 --> 00:11:43.599
+and then it is complex command
+
+00:11:43.600 --> 00:11:45.079
+and it triggers garbage collection
+
+00:11:45.080 --> 00:11:48.079
+but it's not the majority.
+
+00:11:48.080 --> 00:11:51.279
+Again to run the numbers
+
+00:11:51.280 --> 00:11:53.679
+it's better to look into cumulative distribution
+
+00:11:53.680 --> 00:11:56.039
+and see that 50% of garbage collections
+
+00:11:56.040 --> 00:11:58.279
+are basically less than 10 seconds apart.
+
+00:11:58.280 --> 00:12:02.359
+And we can combine it with previous data
+
+00:12:02.360 --> 00:12:07.479
+and we look into whatever garbage collection
+
+00:12:07.480 --> 00:12:09.959
+takes less than 10 seconds from each other
+
+00:12:09.960 --> 00:12:13.119
+and also takes more than say 0.1 seconds.
+
+00:12:13.120 --> 00:12:15.319
+So and then we see that
+
+00:12:15.320 --> 00:12:17.639
+one quarter of all garbage collections
+
+00:12:17.640 --> 00:12:21.039
+are just noticeable and also frequent
+
+00:12:21.040 --> 00:12:23.679
+and 9% are not like
+
+00:12:23.680 --> 00:12:27.199
+more than 0.2% very noticeable and also frequent.
+
+00:12:27.200 --> 00:12:30.079
+So basically it constitutes Emacs freezing.
+
+00:12:30.080 --> 00:12:33.559
+So 9% of all the garbage collection Emacs freezing.
+
+00:12:33.560 --> 00:12:37.319
+Of course if you remember there is a bias
+
+00:12:37.320 --> 00:12:40.519
+but 9% is quite significant number.
+
+00:12:40.520 --> 00:12:44.319
+So garbage collection can really slow down things
+
+00:12:44.320 --> 00:12:48.239
+not for everyone but for significant fraction of users.
+
+00:12:48.240 --> 00:12:52.159
+Another thing I'd like to look into
+
+00:12:52.160 --> 00:12:55.399
+is what I call agglomerated GCs.
+
+00:12:55.400 --> 00:12:57.959
+What I mean by agglomerated is
+
+00:12:57.960 --> 00:13:00.359
+when you have one garbage collection
+
+00:13:00.360 --> 00:13:02.999
+and then another garbage immediately after it.
+
+00:13:03.000 --> 00:13:05.559
+So in terms of numbers I took
+
+00:13:05.560 --> 00:13:08.719
+every subsequent garbage collection
+
+00:13:08.720 --> 00:13:10.399
+which is either immediately after
+
+00:13:10.400 --> 00:13:13.039
+or no more than one second after each.
+
+00:13:13.040 --> 00:13:16.159
+So from point of view of users is like
+
+00:13:16.160 --> 00:13:19.999
+multiple garbage collection they add up together
+
+00:13:20.000 --> 00:13:22.999
+into one giant garbage collection.
+
+00:13:23.000 --> 00:13:25.839
+And if you look into numbers
+
+00:13:25.840 --> 00:13:29.559
+of how many agglomerated garbage collections there are
+
+00:13:29.560 --> 00:13:32.119
+you can see even numbers over 100.
+
+00:13:32.120 --> 00:13:35.479
+So 100 garbage collection going one after another.
+
+00:13:35.480 --> 00:13:39.159
+Even if you think about each garbage collection
+
+00:13:39.160 --> 00:13:42.719
+taking 0.1 second we look into 100 of them
+
+00:13:42.720 --> 00:13:44.639
+it's total 10 seconds.
+
+00:13:44.640 --> 00:13:46.839
+It's like Emacs hanging forever
+
+00:13:46.840 --> 00:13:53.519
+or like a significant number is also 10.
+
+00:13:53.520 --> 00:13:55.999
+So again this would be very annoying to meet such thing.
+
+00:13:56.000 --> 00:13:57.879
+How frequently does it happen?
+
+00:13:57.880 --> 00:14:00.279
+Again we can plot cumulative distribution
+
+00:14:00.280 --> 00:14:03.879
+and we see that 20 percent like 19 percent
+
+00:14:03.880 --> 00:14:07.199
+of all the garbage collection are at least two together
+
+00:14:07.200 --> 00:14:13.679
+and 8 percent like more than 10. So like you think about oh
+
+00:14:13.680 --> 00:14:15.639
+each garbage collection is not taking much time
+
+00:14:15.640 --> 00:14:24.479
+but when you have 10 of them yeah that becomes a problem.
+
+00:14:24.480 --> 00:14:29.919
+Another thing is to answer a question
+
+00:14:29.920 --> 00:14:32.959
+that some people complain about is that
+
+00:14:32.960 --> 00:14:35.799
+longer you use Emacs the slower Emacs become.
+
+00:14:35.800 --> 00:14:43.039
+Of course it may be caused by garbage collection
+
+00:14:43.040 --> 00:14:48.519
+and I wanted to look into how garbage collection time
+
+00:14:48.520 --> 00:14:49.679
+and other statistics,
+
+00:14:49.680 --> 00:14:53.199
+other parameters are evolving over time.
+
+00:14:53.200 --> 00:14:58.559
+And what I can see here is a cumulative distribution
+
+00:14:58.560 --> 00:15:03.719
+of GC duration for like first 10 minutes of Emacs uptime
+
+00:15:03.720 --> 00:15:06.479
+first 100 minutes first 1000 minutes.
+
+00:15:06.480 --> 00:15:10.199
+And if you look closer then you see
+
+00:15:10.200 --> 00:15:14.519
+that each individual garbage collection on average
+
+00:15:14.520 --> 00:15:18.959
+takes longer as you use Emacs longer.
+
+00:15:18.960 --> 00:15:24.039
+However this longer is not much it's like maybe 10 percent
+
+00:15:24.040 --> 00:15:29.479
+like basically garbage collection gets like
+
+00:15:29.480 --> 00:15:34.719
+slow Emacs down more as you use Emacs more but not much.
+
+00:15:34.720 --> 00:15:38.359
+So basically if you do you see Emacs
+
+00:15:38.360 --> 00:15:40.639
+being slower and slower over time
+
+00:15:40.640 --> 00:15:43.159
+it's probably not really garbage collection
+
+00:15:43.160 --> 00:15:45.839
+because it doesn't change too much.
+
+00:15:45.840 --> 00:15:48.119
+And if you look into time
+
+00:15:48.120 --> 00:15:50.839
+between individual garbage collections
+
+00:15:50.840 --> 00:15:53.719
+and you see that the time actually increases
+
+00:15:53.720 --> 00:15:56.719
+as you use Emacs longer which makes sense
+
+00:15:56.720 --> 00:15:58.839
+because initially like first few minutes
+
+00:15:58.840 --> 00:16:01.479
+you have all kind of packages loading
+
+00:16:01.480 --> 00:16:04.239
+like all the port loading and then later
+
+00:16:04.240 --> 00:16:07.239
+everything is loaded and things become more stable.
+
+00:16:07.240 --> 00:16:12.879
+So the conclusion on this part is that
+
+00:16:12.880 --> 00:16:16.399
+if Emacs becomes slower in a long session
+
+00:16:16.400 --> 00:16:18.479
+it's probably not caused by garbage collection.
+
+00:16:18.480 --> 00:16:23.679
+And one word of warning of course is that
+
+00:16:23.680 --> 00:16:27.919
+it's all nice and all when I present the statistics
+
+00:16:27.920 --> 00:16:29.279
+but it's only an average
+
+00:16:29.280 --> 00:16:34.079
+and if you are an actual user like here is one example
+
+00:16:34.080 --> 00:16:37.159
+which shows a total garbage collection time
+
+00:16:37.160 --> 00:16:40.119
+like accumulated together over Emacs uptime
+
+00:16:40.120 --> 00:16:43.199
+and you see different lines
+
+00:16:43.200 --> 00:16:45.559
+which correspond to different sessions of one user
+
+00:16:45.560 --> 00:16:48.679
+and you see they are wildly different
+
+00:16:48.680 --> 00:16:51.439
+like one time there is almost no garbage collection
+
+00:16:51.440 --> 00:16:54.679
+another time you see garbage collection
+
+00:16:54.680 --> 00:16:56.999
+because probably Emacs is used more early
+
+00:16:57.000 --> 00:16:59.599
+or like different pattern of usage
+
+00:16:59.600 --> 00:17:03.159
+and even during a single Emacs session
+
+00:17:03.160 --> 00:17:04.599
+you see a different slope
+
+00:17:04.600 --> 00:17:06.439
+of this curve which means that
+
+00:17:06.440 --> 00:17:09.279
+sometimes garbage collection is infrequent
+
+00:17:09.280 --> 00:17:11.479
+and sometimes it's much more frequent
+
+00:17:11.480 --> 00:17:14.479
+so it's probably much more noticeable one time
+
+00:17:14.480 --> 00:17:15.639
+and less noticeable other time.
+
+00:17:15.640 --> 00:17:19.719
+So if you think about these statistics of course
+
+00:17:19.720 --> 00:17:23.359
+they only represent an average usage
+
+00:17:23.360 --> 00:17:26.359
+but sometimes it can get worse sometimes it can get better.
+
+00:17:26.360 --> 00:17:33.759
+The last parameter I'd like to talk about is
+
+00:17:33.760 --> 00:17:35.799
+garbage collection during Emacs init.
+
+00:17:35.800 --> 00:17:40.439
+Basically if you think about what happens during Emacs init
+
+00:17:40.440 --> 00:17:41.919
+like when Emacs just starting up
+
+00:17:41.920 --> 00:17:44.479
+then whatever garbage collection
+
+00:17:44.480 --> 00:17:46.759
+there it's one or it's several times
+
+00:17:46.760 --> 00:17:51.239
+it all contributes to Emacs taking longer to start.
+
+00:17:51.240 --> 00:17:56.559
+And again we can look into the statistic
+
+00:17:56.560 --> 00:18:01.159
+and see what is the total GC duration after Emacs init
+
+00:18:01.160 --> 00:18:06.159
+and we see that 50% of all the submissions
+
+00:18:06.160 --> 00:18:10.279
+garbage collection adds up more than one second
+
+00:18:10.280 --> 00:18:14.919
+to Emacs init time and for 20% of users
+
+00:18:14.920 --> 00:18:17.079
+it's extra three seconds Emacs start time
+
+00:18:17.080 --> 00:18:18.479
+which is very significant
+
+00:18:18.480 --> 00:18:21.479
+especially for people who are used to Vim
+
+00:18:21.480 --> 00:18:23.919
+which can start in like a fraction of a second
+
+00:18:23.920 --> 00:18:26.239
+and here it just does garbage collection
+
+00:18:26.240 --> 00:18:27.439
+because garbage collection is not
+
+00:18:27.440 --> 00:18:29.239
+everything Emacs does during startup
+
+00:18:29.240 --> 00:18:31.999
+adds up more to the load.
+
+00:18:32.000 --> 00:18:36.119
+Okay that's all nice and all
+
+00:18:36.120 --> 00:18:38.679
+but what can we do about these statistics
+
+00:18:38.680 --> 00:18:40.159
+can we draw any conclusions
+
+00:18:40.160 --> 00:18:43.239
+and the answer is of course
+
+00:18:43.240 --> 00:18:46.079
+like the most important conclusion here is that
+
+00:18:46.080 --> 00:18:49.439
+yes garbage collection can slow down Emacs
+
+00:18:49.440 --> 00:18:52.679
+at least for some people and what to do about it
+
+00:18:52.680 --> 00:18:55.319
+there are two variables which you can tweak
+
+00:18:55.320 --> 00:18:58.719
+it's because gcconce threshold gcconce percentage
+
+00:18:58.720 --> 00:19:03.159
+and having the statistics I can at least look a little bit
+
+00:19:03.160 --> 00:19:08.879
+into what is the effect of increasing these variables
+
+00:19:08.880 --> 00:19:12.439
+like most people just increase gcconce threshold
+
+00:19:12.440 --> 00:19:16.959
+and like all the submissions people did increase
+
+00:19:16.960 --> 00:19:19.919
+and doesn't make much sense to decrease it
+
+00:19:19.920 --> 00:19:21.079
+like to make things worse
+
+00:19:21.080 --> 00:19:27.639
+of course for these statistics
+
+00:19:27.640 --> 00:19:31.559
+the exact values of this increased thresholds
+
+00:19:31.560 --> 00:19:33.839
+are not always the same
+
+00:19:33.840 --> 00:19:36.479
+but at least we can look into some trends
+
+00:19:36.480 --> 00:19:44.759
+so first and obvious thing we can observe
+
+00:19:44.760 --> 00:19:46.759
+is when we compare
+
+00:19:46.760 --> 00:19:50.399
+the standard gc settings standard thresholds
+
+00:19:50.400 --> 00:19:53.999
+and increased thresholds for time between
+
+00:19:54.000 --> 00:19:57.479
+subsequent gcs and as one may expect
+
+00:19:57.480 --> 00:19:59.559
+if you increase the threshold
+
+00:19:59.560 --> 00:20:02.679
+Emacs will do garbage collection less frequently
+
+00:20:02.680 --> 00:20:05.279
+so the spacing between garbage collection increases
+
+00:20:05.280 --> 00:20:07.599
+okay the only thing is that
+
+00:20:07.600 --> 00:20:10.719
+if garbage collection is less frequent
+
+00:20:10.720 --> 00:20:14.079
+then each individual garbage collection becomes longer
+
+00:20:14.080 --> 00:20:18.159
+so if you think about increasing
+
+00:20:18.160 --> 00:20:22.239
+garbage collection thresholds be prepared
+
+00:20:22.240 --> 00:20:26.519
+that in each individual time Emacs freezes will take longer
+
+00:20:26.520 --> 00:20:31.599
+this is one caveat when we talk about
+
+00:20:31.600 --> 00:20:34.079
+this agglomerated gcs which are one after other
+
+00:20:34.080 --> 00:20:36.759
+like if you increase the threshold sufficiently
+
+00:20:36.760 --> 00:20:42.319
+then whatever happened that garbage collections
+
+00:20:42.320 --> 00:20:44.399
+were like done one after other
+
+00:20:44.400 --> 00:20:47.599
+we can now make it so that they are actually separated
+
+00:20:47.600 --> 00:20:51.559
+so like you don't see one giant freeze caused by
+
+00:20:51.560 --> 00:20:52.919
+like 10 gcs in a row
+
+00:20:52.920 --> 00:20:55.759
+instead you can make it so that they are separated
+
+00:20:55.760 --> 00:20:59.079
+and in statistics it's very clear
+
+00:20:59.080 --> 00:21:02.959
+that the number of agglomerated garbage collections
+
+00:21:02.960 --> 00:21:06.919
+decreases dramatically when you increase the thresholds
+
+00:21:06.920 --> 00:21:11.759
+it's particularly evident when we look into startup time
+
+00:21:11.760 --> 00:21:17.279
+if you look at gc duration during Emacs startup
+
+00:21:17.280 --> 00:21:19.159
+and if we look into what happens
+
+00:21:19.160 --> 00:21:20.879
+when you increase the thresholds
+
+00:21:20.880 --> 00:21:23.799
+it's very clear that Emacs startup become faster
+
+00:21:23.800 --> 00:21:26.279
+when you increase gc thresholds
+
+00:21:26.280 --> 00:21:33.359
+so that's all for actual user statistics
+
+00:21:33.360 --> 00:21:35.439
+and now let's try to run into
+
+00:21:35.440 --> 00:21:38.079
+some like actual recommendations
+
+00:21:38.080 --> 00:21:42.639
+on what numbers to set and before we start
+
+00:21:42.640 --> 00:21:44.399
+let me explain a little bit about
+
+00:21:44.400 --> 00:21:46.479
+the difference between these two variables
+
+00:21:46.480 --> 00:21:48.879
+which is gc constant threshold and gc constant percentage
+
+00:21:48.880 --> 00:21:52.359
+so if you think about Emacs memory
+
+00:21:52.360 --> 00:21:55.239
+like there's a certain memory allocated by Emacs
+
+00:21:55.240 --> 00:21:58.479
+and then as you run commands and turn using Emacs
+
+00:21:58.480 --> 00:22:00.079
+there is more memory allocated
+
+00:22:00.080 --> 00:22:04.639
+and Emacs decides when to do garbage collection
+
+00:22:04.640 --> 00:22:06.079
+according these two variables
+
+00:22:06.080 --> 00:22:08.759
+and actually what it does it chooses the larger one
+
+00:22:08.760 --> 00:22:12.119
+so say you have you are late in Emacs session
+
+00:22:12.120 --> 00:22:14.039
+you have a lot of Emacs memory allocated
+
+00:22:14.040 --> 00:22:17.119
+then you have gc constant percentage
+
+00:22:17.120 --> 00:22:19.919
+which is percent of the already allocated memory
+
+00:22:19.920 --> 00:22:25.119
+and that percent is probably going to be the largest
+
+00:22:25.120 --> 00:22:28.319
+because you have more memory
+
+00:22:28.320 --> 00:22:32.559
+and memory means that percent of it is larger
+
+00:22:32.560 --> 00:22:36.359
+so like you have a larger number cost
+
+00:22:36.360 --> 00:22:37.719
+by gc constant percentage
+
+00:22:37.720 --> 00:22:43.079
+so in this scenario when Emacs session is already running
+
+00:22:43.080 --> 00:22:45.319
+for a long time and there is a lot of memory allocated
+
+00:22:45.320 --> 00:22:50.119
+you have gc constant percentage
+
+00:22:50.120 --> 00:22:52.279
+controlling the garbage collection
+
+00:22:52.280 --> 00:22:54.999
+while early in Emacs there is not much memory placed
+
+00:22:55.000 --> 00:22:58.719
+Emacs just starting up then gc constant threshold
+
+00:22:58.720 --> 00:23:01.639
+is controlling how frequently garbage collection happens
+
+00:23:01.640 --> 00:23:04.799
+because smaller allocated memory
+
+00:23:04.800 --> 00:23:06.839
+means its percentage will be a small number
+
+00:23:06.840 --> 00:23:12.319
+so in terms of default values at least
+
+00:23:12.320 --> 00:23:14.239
+gc constant threshold is 800 kilobytes
+
+00:23:14.240 --> 00:23:18.799
+and gc constant percentage is 10
+
+00:23:18.800 --> 00:23:24.159
+so gc constant percentage becomes larger than that threshold
+
+00:23:24.160 --> 00:23:28.919
+when you have more than eight megabytes of allocated memory
+
+00:23:28.920 --> 00:23:31.039
+by Emacs which is quite early
+
+00:23:31.040 --> 00:23:34.279
+and it will probably hold just during the startup
+
+00:23:34.280 --> 00:23:36.799
+and once you start using your maximum
+
+00:23:36.800 --> 00:23:38.919
+and once you load all the histories
+
+00:23:38.920 --> 00:23:42.039
+all the kinds of buffers it's probably going to take
+
+00:23:42.040 --> 00:23:43.959
+more than much more than eight megabytes
+
+00:23:43.960 --> 00:23:50.639
+so now we understand this
+
+00:23:50.640 --> 00:23:53.279
+we can draw certain recommendations
+
+00:23:53.280 --> 00:23:57.279
+about tweaking the gc thresholds
+
+00:23:57.280 --> 00:24:01.159
+so first of all I need to emphasize
+
+00:24:01.160 --> 00:24:03.639
+that any time you increase gc threshold
+
+00:24:03.640 --> 00:24:07.199
+an individual garbage collection time increases
+
+00:24:07.200 --> 00:24:08.759
+so it's not free at all
+
+00:24:08.760 --> 00:24:10.999
+if you don't have problems with garbage collection
+
+00:24:11.000 --> 00:24:13.519
+which is half of the users don't have much problem
+
+00:24:13.520 --> 00:24:15.079
+you don't need to tweak anything
+
+00:24:15.080 --> 00:24:19.359
+only when gc is frequent and slow
+
+00:24:19.360 --> 00:24:23.399
+when Emacs is really really present frequently
+
+00:24:23.400 --> 00:24:27.119
+you may consider increasing gc thresholds only
+
+00:24:27.120 --> 00:24:31.479
+and in particular I recommend
+
+00:24:31.480 --> 00:24:33.279
+increasing gc constant percentage
+
+00:24:33.280 --> 00:24:36.359
+because that's what mostly controls gc
+
+00:24:36.360 --> 00:24:40.079
+when Emacs is running for long session
+
+00:24:40.080 --> 00:24:43.039
+and the numbers are probably like
+
+00:24:43.040 --> 00:24:46.519
+yeah we can estimate the effect of these numbers
+
+00:24:46.520 --> 00:24:49.679
+like for example if you have a default value of 0.1 percent
+
+00:24:49.680 --> 00:24:52.759
+for gc constant percentage 0.1 which is 10 percent
+
+00:24:52.760 --> 00:24:55.039
+and then increase it twice
+
+00:24:55.040 --> 00:24:58.639
+obviously you get twice less frequent gcs
+
+00:24:58.640 --> 00:25:02.559
+but it will come at the cost of extra 10 percent gc time
+
+00:25:02.560 --> 00:25:05.839
+and if you increase 10 times you can think about
+
+00:25:05.840 --> 00:25:08.719
+10 less 10 x less frequent gcs
+
+00:25:08.720 --> 00:25:12.199
+but almost twice longer individual garbage collection time
+
+00:25:12.200 --> 00:25:16.919
+so probably you want to set the number closer to 0.1
+
+00:25:16.920 --> 00:25:23.399
+another part of the users may actually
+
+00:25:23.400 --> 00:25:28.359
+try to optimize Emacs startup time
+
+00:25:28.360 --> 00:25:30.759
+which is quite frequent problem
+
+00:25:30.760 --> 00:25:34.919
+in this case it's probably better to increase gc constant
+
+00:25:34.920 --> 00:25:38.199
+but not too much so like
+
+00:25:38.200 --> 00:25:40.239
+first of all it makes sense to check
+
+00:25:40.240 --> 00:25:43.319
+whether garbage collection is a problem at all
+
+00:25:43.320 --> 00:25:45.999
+during startup and there are two variables
+
+00:25:46.000 --> 00:25:50.199
+which can show what is happening this garbage collection
+
+00:25:50.200 --> 00:25:53.719
+so gc done is a variable that shows
+
+00:25:53.720 --> 00:25:55.039
+how many garbage collection
+
+00:25:55.040 --> 00:26:00.159
+like what is the number of garbage collections triggered
+
+00:26:00.160 --> 00:26:02.599
+like when you check the value
+
+00:26:02.600 --> 00:26:04.039
+or right after you start Emacs
+
+00:26:04.040 --> 00:26:04.799
+you will see that
+
+00:26:04.800 --> 00:26:08.519
+number and gc elapsed variable
+
+00:26:08.520 --> 00:26:11.599
+which gives you a number of seconds
+
+00:26:11.600 --> 00:26:14.959
+which Emacs spent in doing garbage collection
+
+00:26:14.960 --> 00:26:16.879
+so this is probably the most important variable
+
+00:26:16.880 --> 00:26:20.719
+and if you see it's large then you may consider tweaking it
+
+00:26:20.720 --> 00:26:26.799
+for the Emacs startup we can estimate some bounds
+
+00:26:26.800 --> 00:26:30.039
+because in the statistics I never saw anything
+
+00:26:30.040 --> 00:26:32.439
+that is more than 10 seconds extra
+
+00:26:32.440 --> 00:26:34.439
+which even 10 seconds is probably like
+
+00:26:34.440 --> 00:26:39.119
+a really really hard upper bound so
+
+00:26:39.120 --> 00:26:44.479
+or say if you want to decrease the gc contribution
+
+00:26:44.480 --> 00:26:47.479
+like order of magnitude or like two orders of magnitudes
+
+00:26:47.480 --> 00:26:50.879
+let's say like as a really hard top estimate
+
+00:26:50.880 --> 00:26:55.079
+then it corresponds to 80 megabytes gc constant
+
+00:26:55.080 --> 00:26:58.959
+and probably much less so like
+
+00:26:58.960 --> 00:27:00.679
+there's no point setting it
+
+00:27:00.680 --> 00:27:04.159
+to a few hundred megabytes of course
+
+00:27:04.160 --> 00:27:08.439
+there's one caveat which is important to keep in
+
+00:27:08.440 --> 00:27:14.039
+mind though that increasing the gc thresholds
+
+00:27:14.040 --> 00:27:16.399
+is not just increasing individual gc time
+
+00:27:16.400 --> 00:27:20.399
+there's also an actual real impact on the RAM usage
+
+00:27:20.400 --> 00:27:23.839
+so like if you increase gc threshold
+
+00:27:23.840 --> 00:27:26.879
+it increases the RAM usage of Emacs
+
+00:27:26.880 --> 00:27:29.639
+and you shouldn't think that like okay
+
+00:27:29.640 --> 00:27:33.159
+I increased the threshold by like 100 megabytes
+
+00:27:33.160 --> 00:27:37.119
+then 100 megabytes extra RAM usage doesn't matter
+
+00:27:37.120 --> 00:27:38.679
+it's not 100 megabytes
+
+00:27:38.680 --> 00:27:42.319
+because less frequent garbage collection means
+
+00:27:42.320 --> 00:27:45.639
+it will lead to memory fragmentation
+
+00:27:45.640 --> 00:27:50.439
+so in practice if you increase the thresholds
+
+00:27:50.440 --> 00:27:52.799
+to tens or hundreds of megabytes
+
+00:27:52.800 --> 00:27:55.919
+we are talking about gigabytes extra RAM usage
+
+00:27:55.920 --> 00:27:59.719
+for me personally when I tried to play with gc thresholds
+
+00:27:59.720 --> 00:28:02.879
+I have seen Emacs taking two gigabytes like
+
+00:28:02.880 --> 00:28:05.519
+compared to several times less
+
+00:28:05.520 --> 00:28:09.039
+when with default settings so it's not free at all
+
+00:28:09.040 --> 00:28:13.639
+and only like either when you have a lot of free RAM
+
+00:28:13.640 --> 00:28:16.839
+and you don't care or when your Emacs is really slow
+
+00:28:16.840 --> 00:28:19.559
+then you may need to consider this
+
+00:28:19.560 --> 00:28:23.239
+tweaking these defaults so again don't tweak defaults
+
+00:28:23.240 --> 00:28:24.239
+if you don't really have a problem
+
+00:28:24.240 --> 00:28:29.839
+and of course this RAM problem is a big big deal
+
+00:28:29.840 --> 00:28:35.679
+for Emacs devs because from from the point of single user
+
+00:28:35.680 --> 00:28:38.839
+you have like normal laptop most likely like normal PC
+
+00:28:38.840 --> 00:28:42.079
+with a lot of RAM you don't care about these things too much
+
+00:28:42.080 --> 00:28:48.999
+but Emacs in general can run on like all kinds of machines
+
+00:28:49.000 --> 00:28:51.679
+including low-end machines with very limited RAM
+
+00:28:51.680 --> 00:28:55.359
+and anytime Emacs developers consider increasing
+
+00:28:55.360 --> 00:28:57.959
+the defaults for garbage collection
+
+00:28:57.960 --> 00:29:01.479
+it's like they always have to consider
+
+00:29:01.480 --> 00:29:02.959
+if you increase them too much
+
+00:29:02.960 --> 00:29:07.919
+then Emacs may just stop running on certain platforms
+
+00:29:07.920 --> 00:29:14.439
+so that's a very big consideration in terms
+
+00:29:14.440 --> 00:29:16.639
+of the global defaults for everyone
+
+00:29:16.640 --> 00:29:22.199
+although I have to I would say that it might be related
+
+00:29:22.200 --> 00:29:24.479
+to the safe to increase GCCons threshold
+
+00:29:24.480 --> 00:29:27.919
+because it mostly affects startup and during startup
+
+00:29:27.920 --> 00:29:31.279
+it's probably not the peak usage of Emacs
+
+00:29:31.280 --> 00:29:35.599
+and like as Emacs runs for longer
+
+00:29:35.600 --> 00:29:38.199
+it's probably where most of RAM will be used later
+
+00:29:38.200 --> 00:29:44.399
+on the other hand GCCons percentage is much more debating
+
+00:29:44.400 --> 00:29:46.159
+because it has pros and cons
+
+00:29:46.160 --> 00:29:47.719
+it will increase the RAM usage
+
+00:29:47.720 --> 00:29:50.999
+it will increase the individual GC time so
+
+00:29:51.000 --> 00:29:56.119
+if we consider changing it it's much more tricky
+
+00:29:56.120 --> 00:29:59.479
+and we have discussing probably measure the impact on users
+
+00:29:59.480 --> 00:30:05.799
+and a final note on or from the point of view
+
+00:30:05.800 --> 00:30:07.319
+of Emacs development is
+
+00:30:07.320 --> 00:30:11.039
+that this simple mark-and-sweep algorithm
+
+00:30:11.040 --> 00:30:14.119
+is like a very old and not the state-of-the-art algorithm
+
+00:30:14.120 --> 00:30:17.799
+there are variants of garbage collection
+
+00:30:17.800 --> 00:30:19.479
+that are like totally non-blocking
+
+00:30:19.480 --> 00:30:22.479
+so Emacs just doesn't have to freeze
+
+00:30:22.480 --> 00:30:24.279
+during the garbage collection
+
+00:30:24.280 --> 00:30:26.839
+or there are variants of garbage collection algorithm
+
+00:30:26.840 --> 00:30:30.079
+that do not scan all the memory just fraction of it
+
+00:30:30.080 --> 00:30:33.439
+and scan another fraction less frequently
+
+00:30:33.440 --> 00:30:36.999
+so there are actually ways just to change
+
+00:30:37.000 --> 00:30:39.799
+the garbage collection algorithm to make things much faster
+
+00:30:39.800 --> 00:30:44.199
+of course like just changing the numbers of variables
+
+00:30:44.200 --> 00:30:47.079
+like the numbers of variable values
+
+00:30:47.080 --> 00:30:50.079
+is much more tricky and one has to implement it
+
+00:30:50.080 --> 00:30:52.239
+obviously it would be nice if someone implements it
+
+00:30:52.240 --> 00:30:55.639
+but so far it's not happening so yeah it would be nice
+
+00:30:55.640 --> 00:30:59.359
+but maybe not not so quickly
+
+00:30:59.360 --> 00:31:02.159
+there is more chance to change the defaults here
+
+00:31:02.160 --> 00:31:07.479
+to conclude let me reiterate the most important points
+
+00:31:07.480 --> 00:31:11.919
+so from point of view of users you need to understand that
+
+00:31:11.920 --> 00:31:14.479
+yes garbage collection may be a problem
+
+00:31:14.480 --> 00:31:16.679
+but not for everyone so like
+
+00:31:16.680 --> 00:31:21.079
+you should only think about changing the variables
+
+00:31:21.080 --> 00:31:23.559
+when you really know that garbage collection
+
+00:31:23.560 --> 00:31:27.479
+is the problem for you so if you have slow Emacs startup
+
+00:31:27.480 --> 00:31:30.919
+slow Emacs startup and you know that it's caused by
+
+00:31:30.920 --> 00:31:32.479
+garbage collection like by
+
+00:31:32.480 --> 00:31:35.999
+you can check the GC elapsed variable
+
+00:31:36.000 --> 00:31:39.679
+then you may increase GC count threshold
+
+00:31:39.680 --> 00:31:42.119
+like to few tens of megabytes not more
+
+00:31:42.120 --> 00:31:44.479
+it doesn't make sense to increase it much more
+
+00:31:44.480 --> 00:31:48.239
+and if you really have major problems
+
+00:31:48.240 --> 00:31:49.759
+with Emacs being slaggy
+
+00:31:49.760 --> 00:31:52.519
+then you can increase GC count percentage
+
+00:31:52.520 --> 00:31:55.999
+to like 0.2 0.3 maybe
+
+00:31:56.000 --> 00:31:57.679
+one is probably overkill
+
+00:31:57.680 --> 00:32:02.759
+but do watch your Emacs ROM usage it may be really impacted
+
+00:32:02.760 --> 00:32:09.719
+for Emacs developers I'd like to emphasize
+
+00:32:09.720 --> 00:32:12.439
+that there is a real problem with garbage collection
+
+00:32:12.440 --> 00:32:17.959
+and nine percent of all the garbage collection
+
+00:32:17.960 --> 00:32:22.079
+data points we have correspond
+
+00:32:22.080 --> 00:32:24.959
+to really slow noticeable Emacs precision
+
+00:32:24.960 --> 00:32:28.039
+and really frequent less than 10 seconds
+
+00:32:28.040 --> 00:32:32.319
+I'd say that it's really worth
+
+00:32:32.320 --> 00:32:35.279
+increasing GC count threshold at least during startup
+
+00:32:35.280 --> 00:32:40.159
+because it really impacts the Emacs startup time
+
+00:32:40.160 --> 00:32:41.519
+making Emacs startup much faster
+
+00:32:41.520 --> 00:32:44.799
+ideally we need to reimplement
+
+00:32:44.800 --> 00:32:48.599
+the garbage collection algorithm of course it's not easy
+
+00:32:48.600 --> 00:32:50.159
+but it would be really nice
+
+00:32:50.160 --> 00:32:56.399
+and for GC count percentage defaults it's hard to say
+
+00:32:56.400 --> 00:33:00.759
+we may consider changing it but it's up to discussion
+
+00:33:00.760 --> 00:33:03.119
+and we probably need to be conservative here
+
+00:33:03.120 --> 00:33:06.039
+so we came to the end of my talk
+
+00:33:06.040 --> 00:33:09.319
+and this presentation
+
+00:33:09.320 --> 00:33:11.839
+all the data will be available publicly
+
+00:33:11.840 --> 00:33:17.079
+and you can reproduce all the statistic graphs if you wish
+
+00:33:17.080 --> 00:33:21.920
+and thank you for attention