From: Mel Gorman <mgorman@suse.de>
To: Michal Hocko <mhocko@kernel.org>
Cc: linux-mm@kvack.org, Andrew Morton <akpm@linux-foundation.org>,
Johannes Weiner <hannes@cmpxchg.org>,
Vlastimil Babka <vbabka@suse.cz>, Rik van Riel <riel@redhat.com>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 0/7] vm, vmscan: enahance vmscan tracepoints
Date: Fri, 30 Dec 2016 10:20:45 +0000 [thread overview]
Message-ID: <20161230102045.y2fiszc2o2uqmny4@suse.de> (raw)
In-Reply-To: <20161230093654.GC13301@dhcp22.suse.cz>
On Fri, Dec 30, 2016 at 10:36:55AM +0100, Michal Hocko wrote:
> On Fri 30-12-16 09:11:17, Mel Gorman wrote:
> > On Wed, Dec 28, 2016 at 04:30:25PM +0100, Michal Hocko wrote:
> > > Hi,
> > > while debugging [1] I've realized that there is some room for
> > > improvements in the tracepoints set we offer currently. I had hard times
> > > to make any conclusion from the existing ones. The resulting problem
> > > turned out to be active list aging [2] and we are missing at least two
> > > tracepoints to debug such a problem.
> > >
> > > Some existing tracepoints could export more information to see _why_ the
> > > reclaim progress cannot be made not only _how much_ we could reclaim.
> > > The later could be seen quite reasonably from the vmstat counters
> > > already. It can be argued that we are showing too many implementation
> > > details in those tracepoints but I consider them way too lowlevel
> > > already to be usable by any kernel independent userspace. I would be
> > > _really_ surprised if anything but debugging tools have used them.
> > >
> > > Any feedback is highly appreciated.
> > >
> >
> > There is some minor overhead introduced in some paths regardless of
> > whether the tracepoints are active or not but I suspect it's negligible
> > in the context of the overhead of reclaim in general so;
>
> I will work on improving some of them. E.g. I've dropped the change to
> free_hot_cold_page_list because that is indeed a hot path but other than
> that there shouldn't be any even medium hot path which should see any
> overhead I can see. If you are aware of any, please let me know and I
> will think about how to improve it.
>
I didn't spot one. The path where I saw the most overhead is already
quite heavy.
--
Mel Gorman
SUSE Labs
prev parent reply other threads:[~2016-12-30 10:20 UTC|newest]
Thread overview: 48+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-12-28 15:30 [PATCH 0/7] vm, vmscan: enahance vmscan tracepoints Michal Hocko
2016-12-28 15:30 ` [PATCH 1/7] mm, vmscan: remove unused mm_vmscan_memcg_isolate Michal Hocko
2016-12-29 7:33 ` Hillf Danton
2016-12-28 15:30 ` [PATCH 2/7] mm, vmscan: add active list aging tracepoint Michal Hocko
2016-12-29 5:33 ` Minchan Kim
2016-12-29 7:52 ` Michal Hocko
2016-12-30 1:48 ` Minchan Kim
2016-12-30 9:26 ` Michal Hocko
2016-12-30 9:38 ` Hillf Danton
2016-12-30 16:04 ` Minchan Kim
2016-12-30 16:37 ` Michal Hocko
2016-12-30 17:30 ` Michal Hocko
2017-01-03 5:03 ` Minchan Kim
2017-01-03 8:21 ` Michal Hocko
2017-01-04 5:07 ` Minchan Kim
2017-01-04 7:28 ` Vlastimil Babka
2017-01-04 7:50 ` Michal Hocko
2016-12-29 7:44 ` Hillf Danton
2016-12-28 15:30 ` [PATCH 3/7] mm, vmscan: show the number of skipped pages in mm_vmscan_lru_isolate Michal Hocko
2016-12-29 5:53 ` Minchan Kim
2016-12-29 7:49 ` Hillf Danton
2017-01-03 17:21 ` Vlastimil Babka
2017-01-03 20:43 ` Michal Hocko
2016-12-28 15:30 ` [PATCH 4/7] mm, vmscan: show LRU name in mm_vmscan_lru_isolate tracepoint Michal Hocko
2016-12-28 15:50 ` Nikolay Borisov
2016-12-28 16:00 ` Michal Hocko
2016-12-28 16:40 ` Nikolay Borisov
2016-12-28 16:49 ` Michal Hocko
2016-12-29 6:02 ` Minchan Kim
2016-12-29 7:56 ` Michal Hocko
2016-12-30 1:56 ` Minchan Kim
2016-12-30 9:33 ` Michal Hocko
2016-12-29 7:53 ` Hillf Danton
2017-01-03 17:08 ` Vlastimil Babka
2017-01-03 20:47 ` Michal Hocko
2017-01-03 20:52 ` Michal Hocko
2017-01-03 21:24 ` Michal Hocko
2017-01-03 21:40 ` Vlastimil Babka
2017-01-03 21:48 ` Michal Hocko
2016-12-28 15:30 ` [PATCH 5/7] mm, vmscan: extract shrink_page_list reclaim counters into a struct Michal Hocko
2016-12-29 8:00 ` Hillf Danton
2016-12-28 15:30 ` [PATCH 6/7] mm, vmscan: enhance mm_vmscan_lru_shrink_inactive tracepoint Michal Hocko
2016-12-29 8:05 ` Hillf Danton
2016-12-28 15:30 ` [PATCH 7/7] mm, vmscan: add mm_vmscan_inactive_list_is_low tracepoint Michal Hocko
2016-12-29 8:19 ` Hillf Danton
2016-12-30 9:11 ` [PATCH 0/7] vm, vmscan: enahance vmscan tracepoints Mel Gorman
2016-12-30 9:36 ` Michal Hocko
2016-12-30 10:20 ` Mel Gorman [this message]
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