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Re: page fault scalability (ext3, ext4, xfs)

To: Dave Chinner <david@xxxxxxxxxxxxx>
Subject: Re: page fault scalability (ext3, ext4, xfs)
From: David Lang <david@xxxxxxx>
Date: Mon, 19 Aug 2013 16:23:23 -0700 (PDT)
Cc: Jan Kara <jack@xxxxxxx>, Andy Lutomirski <luto@xxxxxxxxxxxxxx>, "Theodore Ts'o" <tytso@xxxxxxx>, Dave Hansen <dave.hansen@xxxxxxxxx>, Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>, Linux FS Devel <linux-fsdevel@xxxxxxxxxxxxxxx>, xfs@xxxxxxxxxxx, "linux-ext4@xxxxxxxxxxxxxxx" <linux-ext4@xxxxxxxxxxxxxxx>, LKML <linux-kernel@xxxxxxxxxxxxxxx>, Tim Chen <tim.c.chen@xxxxxxxxxxxxxxx>, Andi Kleen <ak@xxxxxxxxxxxxxxx>
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In-reply-to: <20130815212826.GS6023@dastard>
References: <520BED7A.4000903@xxxxxxxxx> <20130814230648.GD22316@xxxxxxxxx> <CALCETrVaRQ3WQ5++Uu_0JTaVnjUugAaAhqQK__7r5YWvLxpAhw@xxxxxxxxxxxxxx> <20130815011101.GA3572@xxxxxxxxx> <20130815021028.GM6023@dastard> <CALCETrUfuzgG9U=+eSzCGvbCx-ZskWw+MhQ-qmEyWZK=XWNVmg@xxxxxxxxxxxxxx> <20130815060149.GP6023@dastard> <CALCETrUF+dGhE3qv4LoYmc7A=a+ry93u-d-GgHSAwHXvYN+VNw@xxxxxxxxxxxxxx> <20130815071141.GQ6023@dastard> <20130815074531.GA2147@xxxxxxxxxxxxx> <20130815212826.GS6023@dastard>
User-agent: Alpine 2.02 (DEB 1266 2009-07-14)
On Fri, 16 Aug 2013, Dave Chinner wrote:

The problem with "not exported, don't update" is that files can be
modified on server startup (e.g. after a crash) or in short
maintenance periods when the NFS service is down. When the server is
started back up, the change number needs to indicate the file has
been modified so that clients reconnecting to the server see the
change.

IOWs, even if the NFS server is not up or the filesystem not
exported we still need to update change counts whenever a file
changes if we are going to tell the NFS server that we keep them...

This sounds like you need something more like relctime rather than noctime, something that updates the time in ram, but doesn't insist on flushing it to disk immediatly, updating when convienient or when the file is closed.

David Lang

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