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From: Andrew Morton <akpm@osdl.org>
To: viro@parcelfarce.linux.theplanet.co.uk
Cc: jeffm@novell.com, torvalds@osdl.org, linux-kernel@vger.kernel.org
Subject: Re: [BUG] Race with iput and umount
Date: Sat, 2 Oct 2004 15:23:38 -0700	[thread overview]
Message-ID: <20041002152338.0beb6680.akpm@osdl.org> (raw)
In-Reply-To: <20041002095254.GH23987@parcelfarce.linux.theplanet.co.uk>

viro@parcelfarce.linux.theplanet.co.uk wrote:
>
> the goal of that kludge was to postpone the final
>  iput() past the unlocking the parent for the sake of contention if a wunch
>  of bankers is doing parallel unlink() on files in the same directory

The problematic workloads are much simpler than that: simply a kernel
compile when there's a lot of writeout happening to the same disk.

Truncation of files in /tmp takes a long time because it has to wait for
in-flight writeout.  If we do that synchronous I/O while holding i_sem,
nobody else can get at /tmp.

"When there is a continuous streaming write to the same disk, this patch
reduces the time for `make -j4 bzImage' from 370 seconds to 220."

Yeah, the tweak is not pretty, but that's a significant speedup.

      parent reply	other threads:[~2004-10-02 22:26 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2004-10-02  7:55 Jeff Mahoney
2004-10-02  9:52 ` viro
2004-10-02 15:45   ` Jeff Mahoney
2004-10-02 22:23   ` Andrew Morton [this message]

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