From: Andrew Morton <akpm@linux-foundation.org>
To: Mel Gorman <mel@csn.ul.ie>
Cc: linux-mm@kvack.org, linux-fsdevel@vger.kernel.org,
Linux Kernel List <linux-kernel@vger.kernel.org>,
Johannes Weiner <hannes@cmpxchg.org>,
Minchan Kim <minchan.kim@gmail.com>,
Wu Fengguang <fengguang.wu@intel.com>,
KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Subject: Re: [PATCH 8/8] writeback: Do not sleep on the congestion queue if there are no congested BDIs or if significant congestion is not being encountered in the current zone
Date: Tue, 21 Sep 2010 15:24:33 -0700 [thread overview]
Message-ID: <20100921152433.6edd6a87.akpm@linux-foundation.org> (raw)
In-Reply-To: <20100921221008.GA16323@csn.ul.ie>
On Tue, 21 Sep 2010 23:10:08 +0100
Mel Gorman <mel@csn.ul.ie> wrote:
> On Tue, Sep 21, 2010 at 02:44:13PM -0700, Andrew Morton wrote:
> > On Mon, 20 Sep 2010 10:52:39 +0100
> > Mel Gorman <mel@csn.ul.ie> wrote:
> >
> > > > > This patch tracks how many pages backed by a congested BDI were found during
> > > > > scanning. If all the dirty pages encountered on a list isolated from the
> > > > > LRU belong to a congested BDI, the zone is marked congested until the zone
> > > > > reaches the high watermark.
> > > >
> > > > High watermark, or low watermark?
> > > >
> > >
> > > High watermark. The check is made by kswapd.
> > >
> > > > The terms are rather ambiguous so let's avoid them. Maybe "full"
> > > > watermark and "empty"?
> > > >
> > >
> > > Unfortunately they are ambiguous to me. I know what the high watermark
> > > is but not what the full or empty watermarks are.
> >
> > Really. So what's the "high" watermark?
>
> The high watermark is the point where kswapd goes back to sleep because
> enough pages have been reclaimed. It's a proxy measure for memory pressure.
>
> > From the above text I'm
> > thinking that you mean the high watermark is when the queue has a small
> > number of requests and the low watermark is when the queue has a large
> > number of requests.
> >
>
> I was expecting "zone reaches the high watermark" was the clue that I was
> talking about zone watermarks and not an IO queue but it could be better.
It was more a rant about general terminology rather than one specific case.
> I will try and clarify. How about this as a replacement paragraph?
Works for me, thanks.
WARNING: multiple messages have this Message-ID (diff)
From: Andrew Morton <akpm@linux-foundation.org>
To: Mel Gorman <mel@csn.ul.ie>
Cc: linux-mm@kvack.org, linux-fsdevel@vger.kernel.org,
Linux Kernel List <linux-kernel@vger.kernel.org>,
Johannes Weiner <hannes@cmpxchg.org>,
Minchan Kim <minchan.kim@gmail.com>,
Wu Fengguang <fengguang.wu@intel.com>,
KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Subject: Re: [PATCH 8/8] writeback: Do not sleep on the congestion queue if there are no congested BDIs or if significant congestion is not being encountered in the current zone
Date: Tue, 21 Sep 2010 15:24:33 -0700 [thread overview]
Message-ID: <20100921152433.6edd6a87.akpm@linux-foundation.org> (raw)
In-Reply-To: <20100921221008.GA16323@csn.ul.ie>
On Tue, 21 Sep 2010 23:10:08 +0100
Mel Gorman <mel@csn.ul.ie> wrote:
> On Tue, Sep 21, 2010 at 02:44:13PM -0700, Andrew Morton wrote:
> > On Mon, 20 Sep 2010 10:52:39 +0100
> > Mel Gorman <mel@csn.ul.ie> wrote:
> >
> > > > > This patch tracks how many pages backed by a congested BDI were found during
> > > > > scanning. If all the dirty pages encountered on a list isolated from the
> > > > > LRU belong to a congested BDI, the zone is marked congested until the zone
> > > > > reaches the high watermark.
> > > >
> > > > High watermark, or low watermark?
> > > >
> > >
> > > High watermark. The check is made by kswapd.
> > >
> > > > The terms are rather ambiguous so let's avoid them. Maybe "full"
> > > > watermark and "empty"?
> > > >
> > >
> > > Unfortunately they are ambiguous to me. I know what the high watermark
> > > is but not what the full or empty watermarks are.
> >
> > Really. So what's the "high" watermark?
>
> The high watermark is the point where kswapd goes back to sleep because
> enough pages have been reclaimed. It's a proxy measure for memory pressure.
>
> > From the above text I'm
> > thinking that you mean the high watermark is when the queue has a small
> > number of requests and the low watermark is when the queue has a large
> > number of requests.
> >
>
> I was expecting "zone reaches the high watermark" was the clue that I was
> talking about zone watermarks and not an IO queue but it could be better.
It was more a rant about general terminology rather than one specific case.
> I will try and clarify. How about this as a replacement paragraph?
Works for me, thanks.
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next prev parent reply other threads:[~2010-09-21 22:25 UTC|newest]
Thread overview: 59+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-09-15 12:27 [PATCH 0/8] Reduce latencies and improve overall reclaim efficiency v2 Mel Gorman
2010-09-15 12:27 ` Mel Gorman
2010-09-15 12:27 ` [PATCH 1/8] tracing, vmscan: Add trace events for LRU list shrinking Mel Gorman
2010-09-15 12:27 ` Mel Gorman
2010-09-15 12:27 ` [PATCH 2/8] writeback: Account for time spent congestion_waited Mel Gorman
2010-09-15 12:27 ` Mel Gorman
2010-09-15 12:27 ` [PATCH 3/8] vmscan: Synchronous lumpy reclaim should not call congestion_wait() Mel Gorman
2010-09-15 12:27 ` Mel Gorman
2010-09-15 12:27 ` [PATCH 4/8] vmscan: Narrow the scenarios lumpy reclaim uses synchrounous reclaim Mel Gorman
2010-09-15 12:27 ` Mel Gorman
2010-09-15 12:27 ` [PATCH 5/8] vmscan: Remove dead code in shrink_inactive_list() Mel Gorman
2010-09-15 12:27 ` Mel Gorman
2010-09-15 12:27 ` [PATCH 6/8] vmscan: isolated_lru_pages() stop neighbour search if neighbour cannot be isolated Mel Gorman
2010-09-15 12:27 ` Mel Gorman
2010-09-15 12:27 ` [PATCH 7/8] writeback: Do not sleep on the congestion queue if there are no congested BDIs Mel Gorman
2010-09-15 12:27 ` Mel Gorman
2010-09-16 7:59 ` Minchan Kim
2010-09-16 7:59 ` Minchan Kim
2010-09-16 8:23 ` Mel Gorman
2010-09-16 8:23 ` Mel Gorman
2010-09-15 12:27 ` [PATCH 8/8] writeback: Do not sleep on the congestion queue if there are no congested BDIs or if significant congestion is not being encountered in the current zone Mel Gorman
2010-09-15 12:27 ` Mel Gorman
2010-09-16 8:13 ` Minchan Kim
2010-09-16 8:13 ` Minchan Kim
2010-09-16 9:18 ` Mel Gorman
2010-09-16 9:18 ` Mel Gorman
2010-09-16 14:11 ` Minchan Kim
2010-09-16 14:11 ` Minchan Kim
2010-09-16 15:18 ` Mel Gorman
2010-09-16 15:18 ` Mel Gorman
2010-09-16 22:28 ` Andrew Morton
2010-09-16 22:28 ` Andrew Morton
2010-09-20 9:52 ` Mel Gorman
2010-09-20 9:52 ` Mel Gorman
2010-09-21 21:44 ` Andrew Morton
2010-09-21 21:44 ` Andrew Morton
2010-09-21 22:10 ` Mel Gorman
2010-09-21 22:10 ` Mel Gorman
2010-09-21 22:24 ` Andrew Morton [this message]
2010-09-21 22:24 ` Andrew Morton
2010-09-20 13:05 ` [PATCH] writeback: Do not sleep on the congestion queue if there are no congested BDIs or if significant congestion is not being encounted in the current zone fix Mel Gorman
2010-09-20 13:05 ` Mel Gorman
2010-09-16 22:28 ` [PATCH 0/8] Reduce latencies and improve overall reclaim efficiency v2 Andrew Morton
2010-09-16 22:28 ` Andrew Morton
2010-09-17 7:52 ` Mel Gorman
2010-09-17 7:52 ` Mel Gorman
2010-10-14 15:28 ` Christian Ehrhardt
2010-10-14 15:28 ` Christian Ehrhardt
2010-10-14 15:28 ` Christian Ehrhardt
2010-10-18 13:55 ` Mel Gorman
2010-10-18 13:55 ` Mel Gorman
2010-10-22 12:29 ` Christian Ehrhardt
2010-10-22 12:29 ` Christian Ehrhardt
2010-10-22 12:29 ` Christian Ehrhardt
2010-11-03 10:50 ` Christian Ehrhardt
2010-11-03 10:50 ` Christian Ehrhardt
2010-11-03 10:50 ` Christian Ehrhardt
2010-11-10 14:37 ` Mel Gorman
2010-11-10 14:37 ` Mel Gorman
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