From: Andi Kleen <andi@firstfloor.org>
To: "J. Bruce Fields" <bfields@fieldses.org>
Cc: Andi Kleen <andi@firstfloor.org>,
"Patrick J. LoPresti" <lopresti@gmail.com>,
linux-fsdevel@vger.kernel.org, linux-nfs@vger.kernel.org,
linux-kernel <linux-kernel@vger.kernel.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@fieldses.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
next prev parent reply other threads:[~2010-08-17 18:29 UTC|newest]
Thread overview: 45+ 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
2010-08-13 18:45 ` john stultz
2010-08-13 18:57 ` Patrick J. LoPresti
2010-08-13 19:09 ` john stultz
2010-08-13 20:53 ` Patrick J. LoPresti
2010-08-14 16:45 ` Patrick J. LoPresti
2010-08-15 1:50 ` Bret Towe
2010-08-13 19:57 ` Jim Rees
2010-08-13 20:26 ` john stultz
2010-08-13 20:52 ` Jim Rees
2010-08-17 14:54 ` Andi Kleen
2010-08-17 17:41 ` J. Bruce Fields
2010-08-17 18:29 ` Andi Kleen [this message]
2010-08-17 18:50 ` Patrick J. LoPresti
2010-08-17 19:04 ` J. Bruce Fields
2010-08-17 19:18 ` Patrick J. LoPresti
2010-08-17 19:39 ` Alan Cox
2010-08-17 19:29 ` J. Bruce Fields
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
2010-08-18 18:15 ` Chuck Lever
2010-08-18 23:41 ` Neil Brown
2010-08-19 0:52 ` Neil Brown
2010-08-19 2:08 ` J. Bruce Fields
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
2010-08-17 19:43 ` Patrick J. LoPresti
2010-08-17 19:45 ` J. Bruce Fields
2010-08-18 18:12 ` J. Bruce Fields
2010-08-19 1:41 ` john stultz
2010-08-19 2:31 ` J. Bruce Fields
2010-08-19 3:17 ` john stultz
2010-08-19 22:53 ` J. Bruce Fields
2010-08-18 18:20 ` David Woodhouse
2010-08-18 18:32 ` Patrick J. LoPresti
2010-08-18 18:53 ` Andi Kleen
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