From: Junio C Hamano <gitster@pobox•com>
To: Jonathan Nieder <jrnieder@gmail•com>
Cc: David Kastrup <dak@gnu•org>, Duy Nguyen <pclouds@gmail•com>,
Christian Jaeger <chrjae@gmail•com>,
Git Mailing List <git@vger•kernel.org>
Subject: Re: git gc --aggressive led to about 40 times slower "git log --raw"
Date: Tue, 18 Feb 2014 12:59:43 -0800 [thread overview]
Message-ID: <xmqqzjlocf28.fsf@gitster.dls.corp.google.com> (raw)
In-Reply-To: <20140218155842.GA7855@google.com> (Jonathan Nieder's message of "Tue, 18 Feb 2014 07:59:22 -0800")
Jonathan Nieder <jrnieder@gmail•com> writes:
> David Kastrup wrote:
>> Duy Nguyen <pclouds@gmail•com> writes:
>
>>> Likely because --aggressive passes --depth=250 to pack-objects. Long
>>> delta chains could reduce pack size and increase I/O as well as zlib
>>> processing signficantly.
> [...]
>> Compression should reduce rather than increase the total amount of
>> reads.
>
> --depth=250 means to allow chains of "To get this object, first
> inflate this object, then apply this delta" of length 250.
>
> That's absurdly long, and doesn't even help compression much in
> practice (many short chains referring to the same objects tends to
> work fine). We probably shouldn't make --aggressive do that.
> Something like --depth=10 would make more sense.
Yes, my thinking indeed.
I didn't know --agressive was so aggressive myself, as I personally
never use it. "git repack -a -d -f --depth=32 window=4000" is what I
often use, but I suspect most people would not be patient enough for
that 4k window.
Let's do something like this first and then later make --depth
configurable just like --width, perhaps? For "aggressive", I think
the default width (hardcoded to 250 but configurable) is a bit too
narrow.
builtin/gc.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/builtin/gc.c b/builtin/gc.c
index 6be6c8d..0d010f0 100644
--- a/builtin/gc.c
+++ b/builtin/gc.c
@@ -204,7 +204,7 @@ int cmd_gc(int argc, const char **argv, const char *prefix)
if (aggressive) {
argv_array_push(&repack, "-f");
- argv_array_push(&repack, "--depth=250");
+ argv_array_push(&repack, "--depth=20");
if (aggressive_window > 0)
argv_array_pushf(&repack, "--window=%d", aggressive_window);
}
next prev parent reply other threads:[~2014-02-18 21:00 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-02-18 7:25 git gc --aggressive led to about 40 times slower "git log --raw" Christian Jaeger
2014-02-18 8:55 ` David Kastrup
2014-02-18 9:45 ` Duy Nguyen
2014-02-18 10:25 ` David Kastrup
2014-02-18 15:59 ` Jonathan Nieder
2014-02-18 20:59 ` Junio C Hamano [this message]
2014-02-18 22:46 ` Duy Nguyen
2014-02-19 0:10 ` Junio C Hamano
2014-02-19 0:33 ` Duy Nguyen
2014-02-19 8:38 ` Philippe Vaucher
2014-02-19 9:01 ` David Kastrup
2014-02-19 10:24 ` Duy Nguyen
2014-02-19 10:14 ` Duy Nguyen
2014-02-20 4:09 ` Christian Jaeger
2014-02-20 16:48 ` David Kastrup
2014-02-20 17:06 ` David Kastrup
2014-02-20 18:07 ` David Kastrup
2014-02-19 18:59 ` Junio C Hamano
2014-02-20 23:35 ` Duy Nguyen
2014-02-21 0:32 ` Christian Jaeger
2014-02-21 17:36 ` Junio C Hamano
2014-02-21 5:09 ` Duy Nguyen
2014-02-21 17:47 ` Junio C Hamano
2014-02-24 9:27 ` Philippe Vaucher
2014-02-22 0:36 ` Duy Nguyen
2014-02-22 6:20 ` David Kastrup
2014-02-22 8:53 ` David Kastrup
2014-02-22 9:14 ` Duy Nguyen
2014-02-22 13:00 ` Duy Nguyen
2014-02-22 9:57 ` Andreas Schwab
2014-02-18 16:43 ` Christian Jaeger
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