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From: Junio C Hamano <gitster@pobox.com>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Junio C Hamano <gitster@pobox.com>,
	Dmitry Potapov <dpotapov@gmail.com>,
	Git Mailing List <git@vger.kernel.org>
Subject: Re: [PATCH 3/3] Avoid doing extra 'lstat()'s for d_type if we have an up-to-date cache entry
Date: Thu, 09 Jul 2009 11:34:50 -0700	[thread overview]
Message-ID: <7vbpnt3dth.fsf@alter.siamese.dyndns.org> (raw)
In-Reply-To: <alpine.LFD.2.01.0907090954090.3352@localhost.localdomain> (Linus Torvalds's message of "Thu\, 9 Jul 2009 09\:59\:10 -0700 \(PDT\)")

Linus Torvalds <torvalds@linux-foundation.org> writes:

>> > +		if (!ce_uptodate(ce))
>> > +			break;	/* continue? */
>> 
>> I think this should be continue, as the directory D you are interested in
>> may have two files, one modified, the other uptodate.
>
> The thing is, the directory may have subdirectories, and there may be 
> tens of thousands of files there. And maybe this gets called by code that 
> hasn't done any cache preloading at all, so nothing will be up-to-date.
>
> Do we want to loop over thousands of entries? Or do we want to loop as 
> little as possible, and just say "most of the time the first entry will be 
> representative".

Ah, I see.

It depends on how expensive it is to iterate over an in-core array to
check a single bit (that may not even have been updated) in the cache
entries, compared to an extra lstat().  Perhaps we could autotune that,
but it probably is not worth it. ;-)

  reply	other threads:[~2009-07-09 18:35 UTC|newest]

Thread overview: 39+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2009-07-07  0:05 Too many 'stat' calls by git-status on Windows Dmitry Potapov
2009-07-08 19:49 ` Ramsay Jones
2009-07-09  2:04 ` Linus Torvalds
2009-07-09  2:35   ` Linus Torvalds
2009-07-09  2:40     ` [PATCH 1/3] Add 'fill_directory()' helper function for directory traversal Linus Torvalds
2009-07-09  2:42       ` [PATCH 2/3] Simplify read_directory[_recursive]() arguments Linus Torvalds
2009-07-09  2:43         ` [PATCH 3/3] Avoid doing extra 'lstat()'s for d_type if we have an up-to-date cache entry Linus Torvalds
2009-07-09  8:18           ` Junio C Hamano
2009-07-09 15:52             ` Linus Torvalds
2009-07-09 16:32               ` Junio C Hamano
2009-07-09 16:59                 ` Linus Torvalds
2009-07-09 18:34                   ` Junio C Hamano [this message]
2009-07-09 17:13                 ` Linus Torvalds
2009-07-09 17:18                   ` Linus Torvalds
2009-07-09 18:37                     ` Junio C Hamano
2009-07-09 18:53                       ` Linus Torvalds
2009-07-09 20:44                         ` [PATCH 4/3] Avoid using 'lstat()' to figure out directories Linus Torvalds
2009-07-09 20:47                           ` [PATCH 5/3] Prepare symlink caching for thread-safety Linus Torvalds
2009-07-09 20:48                             ` [PATCH 6/3] Export thread-safe version of 'has_symlink_leading_path()' Linus Torvalds
2009-07-09 20:50                               ` [PATCH 7/3] Make index preloading check the whole path to the file Linus Torvalds
2009-07-09 20:56                                 ` Linus Torvalds
2009-07-10  3:12                                 ` Junio C Hamano
2009-07-10  3:29                                   ` Linus Torvalds
2009-07-10  3:40                                     ` Linus Torvalds
2009-07-11  2:53                                     ` Junio C Hamano
2009-07-11  3:04                                       ` Linus Torvalds
2009-07-12  0:09                               ` [PATCH 6/3] Export thread-safe version of 'has_symlink_leading_path()' Kjetil Barvik
2009-07-12 21:33                                 ` Junio C Hamano
2009-07-09 22:36                           ` [PATCH 4/3] Avoid using 'lstat()' to figure out directories Paolo Bonzini
2009-07-09 23:26                             ` Linus Torvalds
2009-07-09 23:52                               ` Linus Torvalds
2009-07-10  0:13                                 ` Linus Torvalds
2009-07-09 23:37                             ` Junio C Hamano
2009-07-09 21:05                 ` [PATCH 3/3] Avoid doing extra 'lstat()'s for d_type if we have an up-to-date cache entry Dmitry Potapov
2009-07-09 21:52                   ` Eric Blake
2009-07-09 23:30                     ` [PATCH 3/3] Avoid doing extra 'lstat()'s for d_type if we have?an " Dmitry Potapov
2009-07-10 13:04                       ` Dmitry Potapov
2009-07-09 23:29                   ` [PATCH 3/3] Avoid doing extra 'lstat()'s for d_type if we have an " Dmitry Potapov
2009-07-09 13:50           ` Dmitry Potapov

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