Re: Some rough edges of core.fsmonitor

From: Duy Nguyen <pclouds@gmail.com>
Date: Jan 27, 2018, 12:39 UTC
Message-ID: <CACsJy8CJtW3LZ+4Z_06uM4rJO88FXsNvcw+zzVqdFpsQUKrvrg@mail.gmail.com>
In-Reply-To: <87bmhfwmqa.fsf@evledraar.gmail.com>

On Sat, Jan 27, 2018 at 6:43 PM, Ævar Arnfjörð Bjarmason <avarab@gmail.com> wrote:

Show 16 quoted lines

> a) no fsmonitor
>
>     $ time GIT_TRACE_PERFORMANCE=1 ~/g/git/git-status
>     12:32:44.947651 read-cache.c:1890       performance: 0.053153609 s: read cache .git/index
>     12:32:44.967943 preload-index.c:112     performance: 0.020161093 s: preload index
>     12:32:44.974217 read-cache.c:1446       performance: 0.006230611 s: refresh index
>
> ...
>
> b) with fsmonitor
>
>     $ time GIT_TRACE_PERFORMANCE=1 ~/g/git/git-status
>     12:34:23.833625 read-cache.c:1890       performance: 0.049485685 s: read cache .git/index
>     12:34:23.838622 preload-index.c:112     performance: 0.001221197 s: preload index
>     12:34:23.858723 fsmonitor.c:170         performance: 0.020059647 s: fsmonitor process '.git/hooks/fsmonitor-watchman'
>     12:34:23.871532 read-cache.c:1446       performance: 0.032870818 s: refresh index

Hmm.. why does refresh take longer with fsmonitor/watchman? With the help from watchman, we know what files are modified. We don't need manual stat()'ing and this line should be lower than the "no fsmonitor" case, which is 0.006230611s.

>     12:34:23.876427 diff-lib.c:250          performance: 0.004731427 s: diff-files
>     12:34:23.880669 diff-lib.c:527          performance: 0.003944422 s: diff-index
>     12:34:23.899225 dir.c:2290              performance: 0.018509066 s: read directory
>     12:34:23.901914 trace.c:417             performance: 0.118250995 s: git command: '/home/aearnfjord/g/git/git-status'

I don't see any "write index" line here, which is interesting since your case c) is about "don't write index".

> c) with fsmonitor + don't write index

-- 
Duy