From: Ramsay Jones <ramsay@ramsay1.demon.co.uk>
To: Michael Haggerty <mhagger@alum.mit.edu>
Cc: "Junio C Hamano" <gitster@pobox.com>,
"Torsten Bögershausen" <tboegi@web.de>,
"Jeff King" <peff@peff.net>, "Johannes Sixt" <j6t@kdbg.org>,
"Shawn O. Pearce" <spearce@spearce.org>,
mlevedahl@gmail.com, dpotapov@gmail.com,
"GIT Mailing-list" <git@vger.kernel.org>
Subject: Re: [RFC/PATCH 0/1] cygwin: Remove the Win32 l/stat() functions
Date: Wed, 26 Jun 2013 22:45:48 +0100 [thread overview]
Message-ID: <51CB610C.7050501@ramsay1.demon.co.uk> (raw)
In-Reply-To: <51C94425.7050006@alum.mit.edu>
Michael Haggerty wrote:
> On 06/25/2013 07:07 AM, Junio C Hamano wrote:
>> Ramsay Jones <ramsay@ramsay1.demon.co.uk> writes:
>>
>>> Michael Haggerty and Jeff King have been re-vamping the reference
>>> handling code. The failures noted above were provoked by patches
>>> in the 'mh/ref-races' branch. At the time I wrote this patch, that
>>> branch was only included in 'pu', but I notice that this topic has
>>> now progressed to 'next' (see commit 71f1a182).
>>
>> I had an impression that up to 98eeb09e (for_each_ref: load all
>> loose refs before packed refs, 2013-06-20) that is now in 'next'
>> does not agressively use the lstat timestamp of the packed-refs
>> file, and the "optional" bit 5d478f5c (refs: do not invalidate the
>> packed-refs cache unnecessarily, 2013-06-20), and the one in 'next'
>> should be safe with the cheating-lstat. Isn't it the case?
>>
>> In any case, if removing the cheating-lstat will improve the
>> robustness without hurting performance, I am all for it.
>>
>> The less platform specific hacks, the better ;-).
>
> The following patch in the "non-optional" commits (which has already
> been merged to next) uses stat() via the new stat_validity API:
>
> ca9199300e get_packed_ref_cache: reload packed-refs file when it changes
>
> This patch adds some *extra* cache invalidation that was heretofore
> missing. If stat() is broken it could
>
> (a) cause a false positive, resulting in some unnecessary cache
> invalidation and re-reading of packed-refs, which will hurt performance
> but not correctness; or
>
> (b) cause a false negative, in which case the stale cache might be used
> for reading (but not writing), just as was *always* the case before this
> patch.
>
> As far as I understand, the concern for cygwin is (a). I will leave it
> to others to measure and/or decide whether the performance loss is too
> grave to endure until the cygwin stat() situation is fixed.
>
Hmm, I'm not sure I understand ... However, I can confirm that the
'mh/ref-races' branch in next is broken on cygwin. (i.e. it is not
just a speed issue; it provokes fatal errors).
See reply to Junio.
ATB,
Ramsay Jones
next prev parent reply other threads:[~2013-06-26 22:07 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <51C5FD28.1070004@ramsay1.demon.co.uk>
[not found] ` <51C7A875.6020205@gmail.com>
[not found] ` <7va9mf6txq.fsf@alter.siamese.dyndns.org>
2013-06-25 19:23 ` [RFC/PATCH 0/1] cygwin: Remove the Win32 l/stat() functions Johannes Sixt
2013-06-25 20:23 ` Torsten Bögershausen
2013-06-25 21:18 ` Junio C Hamano
2013-06-26 14:19 ` Torsten Bögershausen
2013-06-26 21:54 ` Ramsay Jones
2013-06-27 15:19 ` Torsten Bögershausen
2013-06-27 23:18 ` Ramsay Jones
2013-06-27 2:37 ` Mark Levedahl
[not found] ` <51C6BC4B.9030905@web.de>
[not found] ` <51C8BF2C.2050203@ramsay1.demon.co.uk>
[not found] ` <7vy59y4w3r.fsf@alter.siamese.dyndns.org>
2013-06-26 21:39 ` Ramsay Jones
[not found] ` <51C94425.7050006@alum.mit.edu>
2013-06-26 21:45 ` Ramsay Jones [this message]
2013-06-26 22:35 ` Jeff King
2013-06-26 22:43 ` Jeff King
2013-06-27 22:58 ` Ramsay Jones
2013-06-28 2:31 ` Mark Levedahl
2013-06-27 5:51 ` Michael Haggerty
2013-06-27 19:58 ` Jeff King
2013-06-27 21:04 ` Junio C Hamano
2013-06-27 23:09 ` Ramsay Jones
2013-06-30 17:28 ` Ramsay Jones
2013-06-30 19:50 ` Junio C Hamano
2013-07-04 18:18 ` Ramsay Jones
2013-07-09 11:02 ` Torsten Bögershausen
2013-07-11 17:31 ` Ramsay Jones
2013-06-27 22:17 ` Ramsay Jones
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