From: Johannes Weiner <hannes@cmpxchg.org>
To: Minchan Kim <minchan@kernel.org>
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org,
Andrew Morton <akpm@linux-foundation.org>,
Rik van Riel <riel@redhat.com>, Mel Gorman <mgorman@suse.de>,
Andrea Arcangeli <aarcange@redhat.com>,
Andi Kleen <andi@firstfloor.org>, Michal Hocko <mhocko@suse.cz>,
Tim Chen <tim.c.chen@linux.intel.com>,
kernel-team@fb.com
Subject: Re: [PATCH 01/10] mm: allow swappiness that prefers anon over file
Date: Tue, 7 Jun 2016 10:18:18 -0400 [thread overview]
Message-ID: <20160607141818.GE9978@cmpxchg.org> (raw)
In-Reply-To: <20160607002550.GA26230@bbox>
On Tue, Jun 07, 2016 at 09:25:50AM +0900, Minchan Kim wrote:
> Hi Johannes,
>
> Thanks for the nice work. I didn't read all patchset yet but the design
> makes sense to me so it would be better for zram-based on workload
> compared to as is.
Thanks!
> On Mon, Jun 06, 2016 at 03:48:27PM -0400, Johannes Weiner wrote:
> > --- a/Documentation/sysctl/vm.txt
> > +++ b/Documentation/sysctl/vm.txt
> > @@ -771,14 +771,20 @@ with no ill effects: errors and warnings on these stats are suppressed.)
> >
> > swappiness
> >
> > -This control is used to define how aggressive the kernel will swap
> > -memory pages. Higher values will increase agressiveness, lower values
> > -decrease the amount of swap. A value of 0 instructs the kernel not to
> > -initiate swap until the amount of free and file-backed pages is less
> > -than the high water mark in a zone.
> > +This control is used to define the relative IO cost of cache misses
> > +between the swap device and the filesystem as a value between 0 and
> > +200. At 100, the VM assumes equal IO cost and will thus apply memory
> > +pressure to the page cache and swap-backed pages equally. At 0, the
> > +kernel will not initiate swap until the amount of free and file-backed
> > +pages is less than the high watermark in a zone.
>
> Generally, I agree extending swappiness value good but not sure 200 is
> enough to represent speed gap between file and swap sotrage in every
> cases. - Just nitpick.
How so? You can't give swap more weight than 100%. 200 is the maximum
possible value.
> Some years ago, I extended it to 200 like your patch and experimented it
> based on zram in our platform workload. At that time, it was terribly
> slow in app switching workload if swappiness is higher than 150.
> Although it was highly dependent on the workload, it's dangerous to
> recommend it before fixing balacing between file and anon, I think.
> IOW, I think this patch should be last one in this patchset.
Good point. I'll tone down the recommendations. But OTOH it's a fairly
trivial patch, so I wouldn't want it to close after the current 10/10.
> > The default value is 60.
> >
> > +On non-rotational swap devices, a value of 100 (or higher, depending
> > +on what's backing the filesystem) is recommended.
> > +
> > +For in-memory swap, like zswap, values closer to 200 are recommended.
>
> maybe, like zram
>
> I'm not sure it would be good suggestion for zswap because it ends up
> writing cached pages to swap device once it reaches threshold.
> Then, the cost is compression + decompression + write I/O which is
> heavier than normal swap device(i.e., write I/O). OTOH, zram have no
> (writeback I/O+ decompression) cost.
Oh, good catch. Yeah, I'll change that for v2.
Thanks for your input, Minchan
next prev parent reply other threads:[~2016-06-07 14:18 UTC|newest]
Thread overview: 67+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-06-06 19:48 [PATCH 00/10] mm: balance LRU lists based on relative thrashing Johannes Weiner
2016-06-06 19:48 ` [PATCH 01/10] mm: allow swappiness that prefers anon over file Johannes Weiner
2016-06-07 0:25 ` Minchan Kim
2016-06-07 14:18 ` Johannes Weiner [this message]
2016-06-08 0:06 ` Minchan Kim
2016-06-08 15:58 ` Johannes Weiner
2016-06-09 1:01 ` Minchan Kim
2016-06-09 13:32 ` Johannes Weiner
2016-06-06 19:48 ` [PATCH 02/10] mm: swap: unexport __pagevec_lru_add() Johannes Weiner
2016-06-06 21:32 ` Rik van Riel
2016-06-07 9:07 ` Michal Hocko
2016-06-08 7:14 ` Minchan Kim
2016-06-06 19:48 ` [PATCH 03/10] mm: fold and remove lru_cache_add_anon() and lru_cache_add_file() Johannes Weiner
2016-06-06 21:33 ` Rik van Riel
2016-06-07 9:12 ` Michal Hocko
2016-06-08 7:24 ` Minchan Kim
2016-06-06 19:48 ` [PATCH 04/10] mm: fix LRU balancing effect of new transparent huge pages Johannes Weiner
2016-06-06 21:36 ` Rik van Riel
2016-06-07 9:19 ` Michal Hocko
2016-06-08 7:28 ` Minchan Kim
2016-06-06 19:48 ` [PATCH 05/10] mm: remove LRU balancing effect of temporary page isolation Johannes Weiner
2016-06-06 21:56 ` Rik van Riel
2016-06-06 22:15 ` Johannes Weiner
2016-06-07 1:11 ` Rik van Riel
2016-06-07 13:57 ` Johannes Weiner
2016-06-07 9:26 ` Michal Hocko
2016-06-07 14:06 ` Johannes Weiner
2016-06-07 9:49 ` Michal Hocko
2016-06-08 7:39 ` Minchan Kim
2016-06-08 16:02 ` Johannes Weiner
2016-06-06 19:48 ` [PATCH 06/10] mm: remove unnecessary use-once cache bias from LRU balancing Johannes Weiner
2016-06-07 2:20 ` Rik van Riel
2016-06-07 14:11 ` Johannes Weiner
2016-06-08 8:03 ` Minchan Kim
2016-06-08 12:31 ` Michal Hocko
2016-06-06 19:48 ` [PATCH 07/10] mm: base LRU balancing on an explicit cost model Johannes Weiner
2016-06-06 19:13 ` kbuild test robot
2016-06-07 2:34 ` Rik van Riel
2016-06-07 14:12 ` Johannes Weiner
2016-06-08 8:14 ` Minchan Kim
2016-06-08 16:06 ` Johannes Weiner
2016-06-08 12:51 ` Michal Hocko
2016-06-08 16:16 ` Johannes Weiner
2016-06-09 12:18 ` Michal Hocko
2016-06-09 13:33 ` Johannes Weiner
2016-06-06 19:48 ` [PATCH 08/10] mm: deactivations shouldn't bias the LRU balance Johannes Weiner
2016-06-08 8:15 ` Minchan Kim
2016-06-08 12:57 ` Michal Hocko
2016-06-06 19:48 ` [PATCH 09/10] mm: only count actual rotations as LRU reclaim cost Johannes Weiner
2016-06-08 8:19 ` Minchan Kim
2016-06-08 13:18 ` Michal Hocko
2016-06-06 19:48 ` [PATCH 10/10] mm: balance LRU lists based on relative thrashing Johannes Weiner
2016-06-06 19:22 ` kbuild test robot
2016-06-06 23:50 ` Tim Chen
2016-06-07 16:23 ` Johannes Weiner
2016-06-07 19:56 ` Tim Chen
2016-06-08 13:58 ` Michal Hocko
2016-06-10 2:19 ` Minchan Kim
2016-06-13 15:52 ` Johannes Weiner
2016-06-15 2:23 ` Minchan Kim
2016-06-16 15:12 ` Johannes Weiner
2016-06-17 7:49 ` Minchan Kim
2016-06-17 17:01 ` Johannes Weiner
2016-06-20 7:42 ` Minchan Kim
2016-06-22 21:56 ` Johannes Weiner
2016-06-24 6:22 ` Minchan Kim
2016-06-07 9:51 ` [PATCH 00/10] " Michal Hocko
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