From: Junio C Hamano <gitster@pobox•com>
To: Linus Torvalds <torvalds@linux-foundation•org>
Cc: moe <moe-git@mbox•bz>, git@vger•kernel.org
Subject: Re: git and larger trees, not so fast?
Date: Thu, 09 Aug 2007 11:00:55 -0700 [thread overview]
Message-ID: <7vr6mcy4dk.fsf@assigned-by-dhcp.cox.net> (raw)
In-Reply-To: <alpine.LFD.0.999.0708091015500.25146@woody.linux-foundation.org> (Linus Torvalds's message of "Thu, 9 Aug 2007 10:38:53 -0700 (PDT)")
Linus Torvalds <torvalds@linux-foundation•org> writes:
> So this is all O(n**2), which is why we haven't reacted very much - it
> doesn't show up nearly as much with the kernel. Also, with a smaller set
> of files, it would tends to fit in the L2 cache of most competent CPU's.
> So not only is it n**2, you get the cache trashing behaviour too, and
> that, I think, is what really causes it to fall off the cliff edge!
>
> Gaah. This shouldn't be *that* hard to fix, but I'm not entirely sure I'll
> have time today.
One thing to keep in mind is that in your earlier test of "git
write-tree" (or "git commit") followed by "git add a/file"
followed by "git write-tree" is extremely fast because the
last operation optimizes otherwise O(n) behaviour of write-tree
from index extreamely cheap, thanks to cache-tree in the index.
> Diffing the index against the tree *should* be instantaneous.
Right now we do not cull the subdirectory that we _know_ are
unchanged in "git diff-index --cached" using cache-tree, but
diffing the index against the tree could be instantaneous.
next prev parent reply other threads:[~2007-08-09 18:01 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-08-09 16:30 git and larger trees, not so fast? moe
2007-08-09 17:11 ` Linus Torvalds
2007-08-09 17:38 ` Linus Torvalds
2007-08-09 18:00 ` Junio C Hamano [this message]
2007-08-09 18:06 ` Linus Torvalds
2007-08-09 18:11 ` Junio C Hamano
2007-08-09 20:42 ` Junio C Hamano
2007-08-09 20:52 ` Sean
2007-08-09 21:37 ` Junio C Hamano
2007-08-09 21:41 ` Linus Torvalds
2007-08-09 21:46 ` Linus Torvalds
2007-08-09 22:02 ` Junio C Hamano
2007-08-09 23:38 ` Junio C Hamano
2007-08-10 0:04 ` Junio C Hamano
2007-08-10 0:44 ` Linus Torvalds
2007-08-10 0:51 ` Junio C Hamano
2007-08-10 0:57 ` Linus Torvalds
2007-08-10 3:48 ` Junio C Hamano
2007-08-10 5:55 ` Junio C Hamano
2007-08-10 15:49 ` Linus Torvalds
2007-08-10 16:07 ` Linus Torvalds
2007-08-10 16:51 ` Fix "git commit directory/" performance anomaly Linus Torvalds
2007-08-10 17:14 ` Linus Torvalds
2007-08-10 18:31 ` Junio C Hamano
2007-08-10 18:56 ` Linus Torvalds
2007-08-10 1:42 ` git and larger trees, not so fast? Daniel Barkalow
2007-08-09 17:54 ` Linus Torvalds
2007-08-09 18:06 ` David Kastrup
2007-08-10 19:39 ` Linus Torvalds
2007-08-11 18:47 ` Linus Torvalds
2007-08-11 19:02 ` Fernando J. Pereda
2007-08-11 20:38 ` Linus Torvalds
2007-08-11 20:51 ` Fernando J. Pereda
2007-08-11 22:27 ` Linus Torvalds
2007-08-11 23:26 ` David Kastrup
2007-08-11 20:06 ` moe
2007-08-23 0:30 ` moe
-- strict thread matches above, loose matches on Subject: below --
2007-08-09 16:06 moe
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