From: Andi Kleen <andi-Vw/NltI1exuRpAAqCnN02g@public.gmane.org>
To: "J. Bruce Fields" <bfields-uC3wQj2KruNg9hUCZPvPmw@public.gmane.org>
Cc: Andi Kleen <andi-Vw/NltI1exuRpAAqCnN02g@public.gmane.org>,
"Patrick J. LoPresti"
<lopresti-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>,
linux-fsdevel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
linux-nfs-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
linux-kernel
<linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>
Subject: Re: Proposal: Use hi-res clock for file timestamps
Date: Tue, 17 Aug 2010 20:29:20 +0200 [thread overview]
Message-ID: <20100817182920.GD18161@basil.fritz.box> (raw)
In-Reply-To: <20100817174134.GA23176-uC3wQj2KruNg9hUCZPvPmw@public.gmane.org>
> OK, so that leaves us with the race, even on newer filesystems:
>
> 1. File is modified, mtime updated
> 2. Client fetches mtime to revalidate cache
> 3. File is modified again, mtime updated
> 4. Client fetches new mtime to revalidate cache
You'll always have a race window with time, the only way around
that would be a version number.
> - Tell everyone to use NFSv4 (and make sure we have
> changeattr/i_version working correctly).
> - Use a finer-grained time source. (I believe you when you say
> the TSC is too slow, but maybe we should run some tests to
> make sure.)
It depends on the CPU too.
> - Increment mtime by a nanosecond when necessary.
You cannot be more precise than the backing file system: this causes
non monotonity when the inodes are flushed (has happened in the past)
-Andi
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next prev parent reply other threads:[~2010-08-17 18:29 UTC|newest]
Thread overview: 42+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-08-13 18:25 Proposal: Use hi-res clock for file timestamps Patrick J. LoPresti
[not found] ` <AANLkTimnyXKahtjaFeSsgcq=xMy-pP3na1jidQhZ-dt2-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2010-08-13 18:45 ` john stultz
2010-08-13 18:57 ` Patrick J. LoPresti
2010-08-13 19:09 ` john stultz
[not found] ` <1281726579.2810.10.camel-bi+AKbBUZKY6gyzm1THtWbp2dZbC/Bob@public.gmane.org>
2010-08-13 20:53 ` Patrick J. LoPresti
2010-08-14 16:45 ` Patrick J. LoPresti
2010-08-15 1:50 ` Bret Towe
2010-08-17 14:54 ` Andi Kleen
[not found] ` <87aaolwar8.fsf-3rXA9MLqAseW/qJFnhkgxti2O/JbrIOy@public.gmane.org>
2010-08-17 17:41 ` J. Bruce Fields
[not found] ` <20100817174134.GA23176-uC3wQj2KruNg9hUCZPvPmw@public.gmane.org>
2010-08-17 18:29 ` Andi Kleen [this message]
[not found] ` <20100817182920.GD18161-u0/ZJuX+froe6aEkudXLsA@public.gmane.org>
2010-08-17 18:50 ` Patrick J. LoPresti
2010-08-18 18:20 ` David Woodhouse
2010-08-18 18:32 ` Patrick J. LoPresti
2010-08-18 18:53 ` Andi Kleen
2010-08-17 19:04 ` J. Bruce Fields
[not found] ` <20100817190447.GA28049-uC3wQj2KruNg9hUCZPvPmw@public.gmane.org>
2010-08-17 19:18 ` Patrick J. LoPresti
[not found] ` <AANLkTi=w1UA5ZZDBigpxMiL7A7DnbnQhLkg62JZpC6Ri-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2010-08-17 19:39 ` Alan Cox
[not found] ` <20100817203941.729830b7-qBU/x9rampVanCEyBjwyrvXRex20P6io@public.gmane.org>
2010-08-17 19:29 ` J. Bruce Fields
[not found] ` <20100817192937.GD26609-uC3wQj2KruNg9hUCZPvPmw@public.gmane.org>
2010-08-17 19:52 ` Alan Cox
2010-08-18 5:53 ` Neil Brown
2010-08-18 14:46 ` Patrick J. LoPresti
2010-08-18 17:32 ` J. Bruce Fields
[not found] ` <20100818173203.GC32430-uC3wQj2KruNg9hUCZPvPmw@public.gmane.org>
2010-08-18 18:15 ` Chuck Lever
[not found] ` <0F91AB9D-0E14-4384-ADD6-0A467C3ABFAC-QHcLZuEGTsvQT0dZR+AlfA@public.gmane.org>
2010-08-18 23:41 ` Neil Brown
2010-08-19 0:52 ` Neil Brown
2010-08-19 2:08 ` J. Bruce Fields
[not found] ` <20100819020803.GA30151-uC3wQj2KruNg9hUCZPvPmw@public.gmane.org>
2010-08-19 2:44 ` Neil Brown
2010-08-19 22:46 ` J. Bruce Fields
2010-08-18 23:47 ` Neil Brown
2010-08-18 17:50 ` Andi Kleen
2010-08-18 18:54 ` J. Bruce Fields
2010-08-18 19:25 ` Andi Kleen
2010-08-18 19:30 ` J. Bruce Fields
2010-08-17 19:34 ` Patrick J. LoPresti
2010-08-17 19:54 ` Alan Cox
[not found] ` <20100817205441.200ab9a4-qBU/x9rampVanCEyBjwyrvXRex20P6io@public.gmane.org>
2010-08-17 19:43 ` Patrick J. LoPresti
[not found] ` <AANLkTi=BB-zVFyCLgC+RWai9FFecaOad=pUC2=XFnY3J-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2010-08-17 19:45 ` J. Bruce Fields
2010-08-18 18:12 ` J. Bruce Fields
2010-08-19 1:41 ` john stultz
[not found] ` <AANLkTi=cx31Mgfe7FxJz6LUmTKFR4=9KEBgbFsNLjiSE-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2010-08-19 2:31 ` J. Bruce Fields
[not found] ` <20100819023106.GB30151-uC3wQj2KruNg9hUCZPvPmw@public.gmane.org>
2010-08-19 3:17 ` john stultz
2010-08-19 22:53 ` J. Bruce Fields
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