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From: Duy Nguyen <pclouds@gmail.com>
To: "Ævar Arnfjörð Bjarmason" <avarab@gmail.com>
Cc: git <git@vger.kernel.org>, Ben Peart <benpeart@microsoft.com>,
	Alex Vandiver <alexmv@dropbox.com>,
	Christian Couder <christian.couder@gmail.com>,
	David Turner <dturner@twopensource.com>
Subject: Re: Some rough edges of core.fsmonitor
Date: Sat, 27 Jan 2018 08:36:19 +0700	[thread overview]
Message-ID: <CACsJy8BpO0s6facg+zcKC9icijpefkipM326n6xOArjn=ZW6+w@mail.gmail.com> (raw)
In-Reply-To: <87efmcw3fa.fsf@evledraar.gmail.com>

On Sat, Jan 27, 2018 at 7:28 AM, Ævar Arnfjörð Bjarmason
<avarab@gmail.com> wrote:
> 3) A lot of time spend reading the index (or something..)

I'm resending a patch from my old index-helper series. It should
measure all big time consuming blocks in git. Maybe we should get it
merged...

> While the hook itself takes ~20ms (and watchman itself 1/4 of that)
> status as a whole takes much longer. gprof reveals:
>
>     Each sample counts as 0.01 seconds.
>       %   cumulative   self              self     total
>      time   seconds   seconds    calls  ms/call  ms/call  name
>      15.38      0.02     0.02   221690     0.00     0.00  memihash

This sounds like name-hash to me.

>      15.38      0.04     0.02   221689     0.00     0.00  create_from_disk
>       7.69      0.05     0.01  2216897     0.00     0.00  git_bswap32
>       7.69      0.06     0.01   222661     0.00     0.00  ce_path_match
>       7.69      0.07     0.01   221769     0.00     0.00  hashmap_add
>       7.69      0.08     0.01    39941     0.00     0.00  prep_exclude
>       7.69      0.09     0.01    39940     0.00     0.00  strbuf_addch
>       7.69      0.10     0.01        1    10.00    10.00  read_one
>       7.69      0.11     0.01        1    10.00    10.00  refresh_index
>       7.69      0.12     0.01        1    10.00    10.00  tweak_fsmonitor
>       7.69      0.13     0.01                             preload_thread
>
> The index is 24M in this case, I guess it's unpacking it, but I wonder
> if this couldn't be much faster if we saved away the result of the last
> "status" in something that's quick to access, and then if nothing

No we could do better, we could cache parsed index content so
everybody benefits. I demonstrated it with my "index v254" patch a
while back:

https://public-inbox.org/git/1399980019-8706-1-git-send-email-pclouds@gmail.com/

With the patch I'm sending soon, we can see how much time reading an
index take out of that ~140-150ms (and we probably can cut down index
read time to like 10-20% when cached).

> changed we just report that, and no need to re-write the index (or just
> write the "it was clean at this time" part).

Hmm.. does an index write increase that much time?
-- 
Duy

  reply	other threads:[~2018-01-27  1:36 UTC|newest]

Thread overview: 30+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-01-27  0:28 Some rough edges of core.fsmonitor Ævar Arnfjörð Bjarmason
2018-01-27  1:36 ` Duy Nguyen [this message]
2018-01-27  1:39   ` [PATCH] trace: measure where the time is spent in the index-heavy operations Nguyễn Thái Ngọc Duy
2018-01-27 11:58     ` Thomas Gummerer
2018-01-27 12:27       ` [PATCH v2] " Nguyễn Thái Ngọc Duy
2018-01-27 11:43   ` Some rough edges of core.fsmonitor Ævar Arnfjörð Bjarmason
2018-01-27 12:39     ` Duy Nguyen
2018-01-27 13:09       ` Duy Nguyen
2018-01-27 19:01         ` Ævar Arnfjörð Bjarmason
2018-01-30 22:41           ` Ben Peart
2018-01-29  9:40     ` Duy Nguyen
2018-01-29 23:16       ` Ben Peart
2018-02-01 10:40         ` Duy Nguyen
2018-01-28 20:44 ` Johannes Schindelin
2018-01-28 22:28   ` Ævar Arnfjörð Bjarmason
2018-01-30  1:21     ` Ben Peart
2018-01-31 10:15       ` Duy Nguyen
2018-02-04  9:38         ` [PATCH] dir.c: ignore paths containing .git when invalidating untracked cache Nguyễn Thái Ngọc Duy
2018-02-05 17:44           ` Ben Peart
2018-02-06 12:02             ` Duy Nguyen
2018-02-07  9:21           ` [PATCH v2] " Nguyễn Thái Ngọc Duy
2018-02-07  9:21             ` Nguyễn Thái Ngọc Duy
2018-02-07 16:59               ` Ben Peart
2018-02-13 10:00                 ` Duy Nguyen
2018-02-13 17:57                   ` Junio C Hamano
2018-02-14  1:24                     ` Duy Nguyen
2018-02-14  8:00                       ` Junio C Hamano
2018-01-30 22:57 ` Some rough edges of core.fsmonitor Ben Peart
2018-01-30 23:16   ` Ævar Arnfjörð Bjarmason
2018-01-31 16:12     ` Ben Peart

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