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
WARNING: multiple messages have this Message-ID (diff)
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
--
To unsubscribe from this list: send the line "unsubscribe linux-nfs" in
the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
next prev parent reply other threads:[~2010-08-17 18:29 UTC|newest]
Thread overview: 76+ 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 18:45 ` john stultz
2010-08-13 18:57 ` Patrick J. LoPresti
2010-08-13 19:09 ` john stultz
2010-08-13 19:09 ` john stultz
2010-08-13 20:53 ` Patrick J. LoPresti
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 14:54 ` Andi Kleen
2010-08-17 17:41 ` J. Bruce Fields
2010-08-17 17:41 ` J. Bruce Fields
2010-08-17 18:29 ` Andi Kleen [this message]
2010-08-17 18:29 ` Andi Kleen
2010-08-17 18:50 ` Patrick J. LoPresti
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 19:18 ` Patrick J. LoPresti
2010-08-17 19:39 ` Alan Cox
2010-08-17 19:39 ` Alan Cox
2010-08-17 19:29 ` J. Bruce Fields
2010-08-17 19:29 ` J. Bruce Fields
2010-08-17 19:52 ` Alan Cox
2010-08-17 19:52 ` Alan Cox
2010-08-18 5:53 ` Neil Brown
2010-08-18 5:53 ` Neil Brown
2010-08-18 14:46 ` Patrick J. LoPresti
2010-08-18 14:46 ` Patrick J. LoPresti
2010-08-18 17:32 ` J. Bruce Fields
2010-08-18 17:32 ` J. Bruce Fields
2010-08-18 18:15 ` Chuck Lever
2010-08-18 18:15 ` Chuck Lever
2010-08-18 23:41 ` Neil Brown
2010-08-18 23:41 ` Neil Brown
2010-08-19 0:52 ` Neil Brown
2010-08-19 0:52 ` Neil Brown
2010-08-19 2:08 ` J. Bruce Fields
2010-08-19 2:08 ` J. Bruce Fields
2010-08-19 2:44 ` Neil Brown
2010-08-19 2:44 ` Neil Brown
2010-08-19 22:46 ` J. Bruce Fields
2010-08-19 22:46 ` J. Bruce Fields
2010-08-18 23:47 ` Neil Brown
2010-08-18 23:47 ` Neil Brown
2010-08-18 17:50 ` Andi Kleen
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 19:34 ` Patrick J. LoPresti
2010-08-17 19:54 ` Alan Cox
2010-08-17 19:43 ` Patrick J. LoPresti
2010-08-17 19:43 ` Patrick J. LoPresti
2010-08-17 19:45 ` J. Bruce Fields
2010-08-17 19:45 ` J. Bruce Fields
2010-08-18 18:12 ` J. Bruce Fields
2010-08-18 18:12 ` J. Bruce Fields
2010-08-19 1:41 ` john stultz
2010-08-19 1:41 ` john stultz
2010-08-19 2:31 ` J. Bruce Fields
2010-08-19 2:31 ` J. Bruce Fields
2010-08-19 3:17 ` john stultz
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 18:20 ` David Woodhouse
2010-08-18 18:32 ` Patrick J. LoPresti
2010-08-18 18:32 ` Patrick J. LoPresti
2010-08-18 18:53 ` Andi Kleen
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20100817182920.GD18161@basil.fritz.box \
--to=andi@firstfloor.org \
--cc=bfields@fieldses.org \
--cc=linux-fsdevel@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-nfs@vger.kernel.org \
--cc=lopresti@gmail.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.