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From: Duy Nguyen <pclouds@gmail.com>
To: Ben Peart <peartben@gmail.com>
Cc: Junio C Hamano <gitster@pobox.com>,
	Ben Peart <Ben.Peart@microsoft.com>,
	Git Mailing List <git@vger.kernel.org>
Subject: Re: [PATCH v1] read-cache: speed up index load through parallelization
Date: Fri, 24 Aug 2018 17:37:20 +0200
Message-ID: <CACsJy8CUPGUhR3girstdqD6YVxOQ6_xE+gacT98KXgqOSPz0dw@mail.gmail.com> (raw)
In-Reply-To: <4c70ea50-5b43-8696-3c46-cf3d658a0ef8@gmail.com>

Since we're cutting corners to speed things up, could you try
something like this?

I notice that reading v4 is significantly slower than v2 and
apparently strlen() (at least from glibc) is much cleverer and at
least gives me a few percentage time saving.

diff --git a/read-cache.c b/read-cache.c
index 7b1354d759..d10cccaed0 100644
--- a/read-cache.c
+++ b/read-cache.c
@@ -1755,8 +1755,7 @@ static unsigned long expand_name_field(struct
strbuf *name, const char *cp_)
        if (name->len < len)
                die("malformed name field in the index");
        strbuf_remove(name, name->len - len, len);
-       for (ep = cp; *ep; ep++)
-               ; /* find the end */
+       ep = cp + strlen(cp);
        strbuf_add(name, cp, ep - cp);
        return (const char *)ep + 1 - cp_;
 }

On Thu, Aug 23, 2018 at 10:36 PM Ben Peart <peartben@gmail.com> wrote:
> > Nice to see this done without a new index extension that records
> > offsets, so that we can load existing index files in parallel.
> >
>
> Yes, I prefer this simpler model as well.  I wasn't sure it would
> produce a significant improvement given the primary thread still has to
> run through the variable length cache entries but was pleasantly surprised.

Out of curiosity, how much time saving could we gain by recording
offsets as an extension (I assume we need, like 4 offsets if the
system has 4 cores)? Much much more than this simpler model (which may
justify the complexity) or just "meh" compared to this?
-- 
Duy

  reply index

Thread overview: 199+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-08-23 15:41 Ben Peart
2018-08-23 17:31 ` Stefan Beller
2018-08-23 19:44   ` Ben Peart
2018-08-24 18:40   ` Duy Nguyen
2018-08-28 14:53     ` Ben Peart
2018-08-23 18:06 ` Junio C Hamano
2018-08-23 20:33   ` Ben Peart
2018-08-24 15:37     ` Duy Nguyen [this message]
2018-08-24 15:57       ` Duy Nguyen
2018-08-24 17:28         ` Ben Peart
2018-08-25  6:44         ` [PATCH] read-cache.c: optimize reading index format v4 Nguyễn Thái Ngọc Duy
2018-08-27 19:36           ` Junio C Hamano
2018-08-28 19:25             ` Duy Nguyen
2018-08-28 23:54               ` Ben Peart
2018-08-29 17:14               ` Junio C Hamano
2018-09-04 16:08             ` Duy Nguyen
2018-09-02 13:19           ` [PATCH v2 0/1] " Nguyễn Thái Ngọc Duy
2018-09-02 13:19             ` [PATCH v2 1/1] read-cache.c: " Nguyễn Thái Ngọc Duy
2018-09-04 18:58               ` Junio C Hamano
2018-09-04 19:31               ` Junio C Hamano
2018-08-24 18:20       ` [PATCH v1] read-cache: speed up index load through parallelization Duy Nguyen
2018-08-24 18:40         ` Ben Peart
2018-08-24 19:00           ` Duy Nguyen
2018-08-24 19:57             ` Ben Peart
2018-08-29 15:25 ` [PATCH v2 0/3] " Ben Peart
2018-08-29 15:25   ` [PATCH v2 1/3] " Ben Peart
2018-08-29 17:14     ` Junio C Hamano
2018-08-29 21:35       ` Ben Peart
2018-09-03 19:16     ` Duy Nguyen
2018-08-29 15:25   ` [PATCH v2 2/3] read-cache: load cache extensions on worker thread Ben Peart
2018-08-29 17:12     ` Junio C Hamano
2018-08-29 21:42       ` Ben Peart
2018-08-29 22:19         ` Junio C Hamano
2018-09-03 19:21     ` Duy Nguyen
2018-09-03 19:27       ` Duy Nguyen
2018-08-29 15:25   ` [PATCH v2 3/3] read-cache: micro-optimize expand_name_field() to speed up V4 index parsing Ben Peart
2018-09-06 21:03 ` [PATCH v3 0/4] read-cache: speed up index load through parallelization Ben Peart
2018-09-06 21:03   ` [PATCH v3 1/4] read-cache: optimize expand_name_field() to speed up V4 index parsing Ben Peart
2018-09-06 21:03   ` [PATCH v3 2/4] eoie: add End of Index Entry (EOIE) extension Ben Peart
2018-09-07 17:55     ` Junio C Hamano
2018-09-07 20:23       ` Ben Peart
2018-09-08  6:29         ` Martin Ågren
2018-09-08 14:03           ` Ben Peart
2018-09-08 17:08             ` Martin Ågren
2018-09-06 21:03   ` [PATCH v3 3/4] read-cache: load cache extensions on a worker thread Ben Peart
2018-09-07 21:10     ` Junio C Hamano
2018-09-08 14:56       ` Ben Peart
2018-09-06 21:03   ` [PATCH v3 4/4] read-cache: speed up index load through parallelization Ben Peart
2018-09-07  4:16     ` Torsten Bögershausen
2018-09-07 13:43       ` Ben Peart
2018-09-07 17:21   ` [PATCH v3 0/4] " Junio C Hamano
2018-09-07 18:31     ` Ben Peart
2018-09-08 13:18     ` Duy Nguyen
2018-09-11 23:26 ` [PATCH v4 0/5] " Ben Peart
2018-09-11 23:26   ` [PATCH v4 1/5] eoie: add End of Index Entry (EOIE) extension Ben Peart
2018-09-11 23:26   ` [PATCH v4 2/5] read-cache: load cache extensions on a worker thread Ben Peart
2018-09-11 23:26   ` [PATCH v4 3/5] read-cache: speed up index load through parallelization Ben Peart
2018-09-11 23:26   ` [PATCH v4 4/5] read-cache.c: optimize reading index format v4 Ben Peart
2018-09-11 23:26   ` [PATCH v4 5/5] read-cache: clean up casting and byte decoding Ben Peart
2018-09-12 14:34   ` [PATCH v4 0/5] read-cache: speed up index load through parallelization Ben Peart
2018-09-12 16:18 ` [PATCH v5 " Ben Peart
2018-09-12 16:18   ` [PATCH v5 1/5] eoie: add End of Index Entry (EOIE) extension Ben Peart
2018-09-13 22:44     ` Junio C Hamano
2018-09-15 10:02     ` Duy Nguyen
2018-09-17 14:54       ` Ben Peart
2018-09-17 16:05         ` Duy Nguyen
2018-09-17 17:31           ` Junio C Hamano
2018-09-17 17:38             ` Duy Nguyen
2018-09-17 19:08               ` Junio C Hamano
2018-09-12 16:18   ` [PATCH v5 2/5] read-cache: load cache extensions on a worker thread Ben Peart
2018-09-15 10:22     ` Duy Nguyen
2018-09-15 10:24       ` Duy Nguyen
2018-09-17 16:38         ` Ben Peart
2018-09-15 16:23       ` Duy Nguyen
2018-09-17 17:19         ` Junio C Hamano
2018-09-17 16:26       ` Ben Peart
2018-09-17 16:45         ` Duy Nguyen
2018-09-17 21:32       ` Junio C Hamano
2018-09-12 16:18   ` [PATCH v5 3/5] read-cache: load cache entries on worker threads Ben Peart
2018-09-15 10:31     ` Duy Nguyen
2018-09-17 17:25       ` Ben Peart
2018-09-15 11:07     ` Duy Nguyen
2018-09-15 11:09       ` Duy Nguyen
2018-09-17 18:52         ` Ben Peart
2018-09-15 11:29     ` Duy Nguyen
2018-09-12 16:18   ` [PATCH v5 4/5] read-cache.c: optimize reading index format v4 Ben Peart
2018-09-12 16:18   ` [PATCH v5 5/5] read-cache: clean up casting and byte decoding Ben Peart
2018-09-26 19:54 ` [PATCH v6 0/7] speed up index load through parallelization Ben Peart
2018-09-26 19:54   ` [PATCH v6 1/7] read-cache.c: optimize reading index format v4 Ben Peart
2018-09-26 19:54   ` [PATCH v6 2/7] read-cache: clean up casting and byte decoding Ben Peart
2018-09-26 19:54   ` [PATCH v6 3/7] eoie: add End of Index Entry (EOIE) extension Ben Peart
2018-09-28  0:19     ` SZEDER Gábor
2018-09-28 18:38       ` Ben Peart
2018-09-29  0:51     ` SZEDER Gábor
2018-09-29  5:45     ` Duy Nguyen
2018-09-29 18:24       ` Junio C Hamano
2018-09-26 19:54   ` [PATCH v6 4/7] config: add new index.threads config setting Ben Peart
2018-09-28  0:26     ` SZEDER Gábor
2018-09-28 13:39       ` Ben Peart
2018-09-28 17:07         ` Junio C Hamano
2018-09-28 19:41           ` Ben Peart
2018-09-28 20:30             ` Ramsay Jones
2018-09-28 22:15               ` Junio C Hamano
2018-10-01 13:17                 ` Ben Peart
2018-10-01 15:06                   ` SZEDER Gábor
2018-09-26 19:54   ` [PATCH v6 5/7] read-cache: load cache extensions on a worker thread Ben Peart
2018-09-26 19:54   ` [PATCH v6 6/7] ieot: add Index Entry Offset Table (IEOT) extension Ben Peart
2018-09-26 19:54   ` [PATCH v6 7/7] read-cache: load cache entries on worker threads Ben Peart
2018-09-26 22:06   ` [PATCH v6 0/7] speed up index load through parallelization Junio C Hamano
2018-09-27 17:13   ` Duy Nguyen
2018-10-01 13:45 ` [PATCH v7 " Ben Peart
2018-10-01 13:45   ` [PATCH v7 1/7] read-cache.c: optimize reading index format v4 Ben Peart
2018-10-01 13:45   ` [PATCH v7 2/7] read-cache: clean up casting and byte decoding Ben Peart
2018-10-01 15:10     ` Duy Nguyen
2018-10-01 13:45   ` [PATCH v7 3/7] eoie: add End of Index Entry (EOIE) extension Ben Peart
2018-10-01 15:17     ` SZEDER Gábor
2018-10-02 14:34       ` Ben Peart
2018-10-01 15:30     ` Duy Nguyen
2018-10-02 15:13       ` Ben Peart
2018-10-01 13:45   ` [PATCH v7 4/7] config: add new index.threads config setting Ben Peart
2018-10-01 13:45   ` [PATCH v7 5/7] read-cache: load cache extensions on a worker thread Ben Peart
2018-10-01 15:50     ` Duy Nguyen
2018-10-02 15:00       ` Ben Peart
2018-10-01 13:45   ` [PATCH v7 6/7] ieot: add Index Entry Offset Table (IEOT) extension Ben Peart
2018-10-01 16:27     ` Duy Nguyen
2018-10-02 16:34       ` Ben Peart
2018-10-02 17:02         ` Duy Nguyen
2018-10-01 13:45   ` [PATCH v7 7/7] read-cache: load cache entries on worker threads Ben Peart
2018-10-01 17:09     ` Duy Nguyen
2018-10-02 19:09       ` Ben Peart
2018-10-10 15:59 ` [PATCH v8 0/7] speed up index load through parallelization Ben Peart
2018-10-10 15:59   ` [PATCH v8 1/7] read-cache.c: optimize reading index format v4 Ben Peart
2018-10-10 15:59   ` [PATCH v8 2/7] read-cache: clean up casting and byte decoding Ben Peart
2018-10-10 15:59   ` [PATCH v8 3/7] eoie: add End of Index Entry (EOIE) extension Ben Peart
2018-10-10 15:59   ` [PATCH v8 4/7] config: add new index.threads config setting Ben Peart
2018-10-10 15:59   ` [PATCH v8 5/7] read-cache: load cache extensions on a worker thread Ben Peart
2018-10-10 15:59   ` [PATCH v8 6/7] ieot: add Index Entry Offset Table (IEOT) extension Ben Peart
2018-10-10 15:59   ` [PATCH v8 7/7] read-cache: load cache entries on worker threads Ben Peart
2018-10-19 16:11     ` Jeff King
2018-10-22  2:14       ` Junio C Hamano
2018-10-22 14:40         ` Ben Peart
2018-10-12  3:18   ` [PATCH v8 0/7] speed up index load through parallelization Junio C Hamano
2018-10-14 12:28   ` Duy Nguyen
2018-10-15 17:33     ` Ben Peart
2018-11-13  0:38   ` [PATCH 0/3] Avoid confusing messages from new index extensions (Re: [PATCH v8 0/7] speed up index load through parallelization) Jonathan Nieder
2018-11-13  0:39     ` [PATCH 1/3] eoie: default to not writing EOIE section Jonathan Nieder
2018-11-13  1:05       ` Junio C Hamano
2018-11-13 15:14         ` Ben Peart
2018-11-13 18:25           ` Jonathan Nieder
2018-11-14  1:36             ` Junio C Hamano
2018-11-15  0:19               ` Jonathan Nieder
2018-11-13  0:39     ` [PATCH 2/3] ieot: default to not writing IEOT section Jonathan Nieder
2018-11-13  0:58       ` Jonathan Tan
2018-11-13  1:09       ` Junio C Hamano
2018-11-13  1:12         ` Jonathan Nieder
2018-11-13 15:37           ` Duy Nguyen
2018-11-13 18:09         ` Jonathan Nieder
2018-11-13 15:22       ` Ben Peart
2018-11-13 18:18         ` Jonathan Nieder
2018-11-13 19:15           ` Ben Peart
2018-11-13 21:08             ` Jonathan Nieder
2018-11-14 18:09               ` Ben Peart
2018-11-15  0:05                 ` Jonathan Nieder
2018-11-14  3:05         ` Junio C Hamano
2018-11-20  6:09           ` [PATCH v2 0/5] Avoid confusing messages from new index extensions Jonathan Nieder
2018-11-20  6:11             ` [PATCH 1/5] eoie: default to not writing EOIE section Jonathan Nieder
2018-11-20 13:06               ` Ben Peart
2018-11-20 13:21                 ` SZEDER Gábor
2018-11-21 16:46                   ` Jeff King
2018-11-22  0:47                     ` Junio C Hamano
2018-11-20 15:01               ` Ben Peart
2018-11-20  6:12             ` [PATCH 2/5] ieot: default to not writing IEOT section Jonathan Nieder
2018-11-20 13:07               ` Ben Peart
2018-11-26 19:59                 ` Stefan Beller
2018-11-26 21:47                   ` Ben Peart
2018-11-26 22:02                     ` Stefan Beller
2018-11-27  0:50                   ` Junio C Hamano
2018-11-20  6:12             ` [PATCH 3/5] index: do not warn about unrecognized extensions Jonathan Nieder
2018-11-20  6:14             ` [PATCH 4/5] index: make index.threads=true enable ieot and eoie Jonathan Nieder
2018-11-20 13:24               ` Ben Peart
2018-11-20  6:15             ` [PATCH 5/5] index: offer advice for unknown index extensions Jonathan Nieder
2018-11-20  9:26               ` Ævar Arnfjörð Bjarmason
2018-11-20 13:30                 ` Ben Peart
2018-11-21  0:22                   ` Junio C Hamano
2018-11-21  0:39                     ` Jonathan Nieder
2018-11-21  0:44                       ` Jonathan Nieder
2018-11-21  5:01                       ` Junio C Hamano
2018-11-21  5:04                         ` Jonathan Nieder
2018-11-21  5:15                         ` Junio C Hamano
2018-11-21  5:31                           ` Junio C Hamano
2018-11-21  1:03                     ` Jonathan Nieder
2018-11-21  4:23                       ` Junio C Hamano
2018-11-21  4:57                         ` Jonathan Nieder
2018-11-21  9:30                       ` Ævar Arnfjörð Bjarmason
2018-11-13  0:40     ` [PATCH 3/3] index: do not warn about unrecognized extensions Jonathan Nieder
2018-11-13  1:10       ` Junio C Hamano
2018-11-13 15:25       ` Ben Peart
2018-11-14  3:24       ` Junio C Hamano
2018-11-14 18:19         ` Ben Peart

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