From: Andrew Morton <akpm@osdl.org>
To: Ravikiran G Thirumalai <kiran@scalex86.org>
Cc: linux-kernel@vger.kernel.org
Subject: Re: [patch] mm: Convert global dirty_exceeded flag to per-node node_dirty_exceeded
Date: Mon, 16 Jan 2006 18:13:23 -0800 [thread overview]
Message-ID: <20060116181323.7a5f0ac7.akpm@osdl.org> (raw)
In-Reply-To: <20060117020352.GB5313@localhost.localdomain>
Ravikiran G Thirumalai <kiran@scalex86.org> wrote:
>
> This is a repost. I did not get any comments when I last posted this
> about a month back. So I guess this patch is all good :)
>
I thought it was fairly ghastly, sorry ;)
> Convert global dirty_exceeded flag to per-node node_dirty_exceeded.
>
> dirty_exceeded ping pongs between nodes in order to force all cpus in
> the system to increase the frequency of calls to balance_dirty_pages.
>
> Currently dirty_exceeded is used by balance_dirty_pages_ratelimited to
> force all CPUs in the system call balance_dirty_pages often, in order to
> reduce the amount of dirty pages in the entire system (based on
> dirty_thresh and one CPU exceeding thee ratelimits). As dirty_exceeded
> is a global variable, it will ping-pong between nodes of a NUMA system
> which is not good.
Did you not test this obvious little optimisation?
--- devel/mm/page-writeback.c~mm-dirty_exceeded-speedup 2006-01-16 18:11:36.000000000 -0800
+++ devel-akpm/mm/page-writeback.c 2006-01-16 18:11:56.000000000 -0800
@@ -212,7 +212,8 @@ static void balance_dirty_pages(struct a
if (nr_reclaimable + wbs.nr_writeback <= dirty_thresh)
break;
- dirty_exceeded = 1;
+ if (!dirty_exceeded)
+ dirty_exceeded = 1;
/* Note: nr_reclaimable denotes nr_dirty + nr_unstable.
* Unstable writes are a feature of certain networked
@@ -234,7 +235,7 @@ static void balance_dirty_pages(struct a
blk_congestion_wait(WRITE, HZ/10);
}
- if (nr_reclaimable + wbs.nr_writeback <= dirty_thresh)
+ if (nr_reclaimable + wbs.nr_writeback <= dirty_thresh && dirty_exceeded)
dirty_exceeded = 0;
if (writeback_in_progress(bdi))
_
next prev parent reply other threads:[~2006-01-17 2:13 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-01-17 2:03 [patch] mm: Convert global dirty_exceeded flag to per-node node_dirty_exceeded Ravikiran G Thirumalai
2006-01-17 2:13 ` Andrew Morton [this message]
2006-01-18 1:29 ` Ravikiran G Thirumalai
2006-01-18 2:09 ` Andrew Morton
2006-01-18 3:09 ` Ravikiran G Thirumalai
2006-01-18 3:22 ` Andrew Morton
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