Date: Sat, 2 Oct 2004 15:23:38 -0700
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
Message-Id: <20041002152338.0beb6680.akpm@osdl.org>
In-Reply-To: <20041002095254.GH23987@parcelfarce.linux.theplanet.co.uk>
References: <415E5EE6.3010800@novell.com>
	<20041002095254.GH23987@parcelfarce.linux.theplanet.co.uk>
Mime-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 1013
Lines: 22

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.
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/