Date: Tue, 10 Jan 2006 21:46:48 -0800
From: Andrew Morton <akpm@osdl.org>
To: Christoph Lameter <clameter@sgi.com>
Cc: cpw@sgi.com, linux-kernel@vger.kernel.org, clameter@sgi.com,
       lhms-devel@lists.sourceforge.net, taka@valinux.co.jp,
       kamezawa.hiroyu@jp.fujitsu.com
Subject: Re: [PATCH 2/5] Direct Migration V9: migrate_pages() extension
Message-Id: <20060110214648.4d54da7c.akpm@osdl.org>
In-Reply-To: <20060110224124.19138.36811.sendpatchset@schroedinger.engr.sgi.com>
References: <20060110224114.19138.10463.sendpatchset@schroedinger.engr.sgi.com>
	<20060110224124.19138.36811.sendpatchset@schroedinger.engr.sgi.com>
Mime-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 1052
Lines: 29

Christoph Lameter <clameter@sgi.com> wrote:
>
> +	for(i = 0; i < 10 && page_mapped(page); i++) {
>  +		int rc = try_to_unmap(page);
>  +
>  +		if (rc == SWAP_SUCCESS)
>  +			break;
>  +		/*
>  +		 * If there are other runnable processes then running
>  +		 * them may make it possible to unmap the page
>  +		 */
>  +		schedule();
>  +	}

The schedule() in state TASK_RUNNING simply won't do anything unless this
process happens to have been preempted.  You'll find that an ndelay(100) is
about as useful.

So I'd suggest that this part needs a bit of a rethink.  If we really need
to run other processes then try a schedule_timeout_uninterruptible(1).  If
not, just remove the loop.

Please stick a printk in there, work out how often and under which
workloads that loop is actually doing something useful.
-
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/