From: Andrew Morton <akpm@linux-foundation.org>
To: js1304@gmail.com
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org,
Johannes Weiner <hannes@cmpxchg.org>,
Michal Hocko <mhocko@kernel.org>, Hugh Dickins <hughd@google.com>,
Minchan Kim <minchan@kernel.org>,
Vlastimil Babka <vbabka@suse.cz>,
Mel Gorman <mgorman@techsingularity.net>,
kernel-team@lge.com, Joonsoo Kim <iamjoonsoo.kim@lge.com>
Subject: Re: [PATCH v2 0/9] workingset protection/detection on the anonymous LRU list
Date: Wed, 26 Feb 2020 19:39:42 -0800 [thread overview]
Message-ID: <20200226193942.30049da9c090b466bdc5ec23@linux-foundation.org> (raw)
In-Reply-To: <1582175513-22601-1-git-send-email-iamjoonsoo.kim@lge.com>
On Thu, 20 Feb 2020 14:11:44 +0900 js1304@gmail.com wrote:
> From: Joonsoo Kim <iamjoonsoo.kim@lge.com>
>
> Hello,
>
> This patchset implements workingset protection and detection on
> the anonymous LRU list.
The test robot measurement got my attention!
http://lkml.kernel.org/r/20200227022905.GH6548@shao2-debian
> * Changes on v2
> - fix a critical bug that uses out of index lru list in
> workingset_refault()
> - fix a bug that reuses the rotate value for previous page
>
> * SUBJECT
> workingset protection
>
> * PROBLEM
> In current implementation, newly created or swap-in anonymous page is
> started on the active list. Growing the active list results in rebalancing
> active/inactive list so old pages on the active list are demoted to the
> inactive list. Hence, hot page on the active list isn't protected at all.
>
> Following is an example of this situation.
>
> Assume that 50 hot pages on active list and system can contain total
> 100 pages. Numbers denote the number of pages on active/inactive
> list (active | inactive). (h) stands for hot pages and (uo) stands for
> used-once pages.
>
> 1. 50 hot pages on active list
> 50(h) | 0
>
> 2. workload: 50 newly created (used-once) pages
> 50(uo) | 50(h)
>
> 3. workload: another 50 newly created (used-once) pages
> 50(uo) | 50(uo), swap-out 50(h)
>
> As we can see, hot pages are swapped-out and it would cause swap-in later.
>
> * SOLUTION
> Since this is what we want to avoid, this patchset implements workingset
> protection. Like as the file LRU list, newly created or swap-in anonymous
> page is started on the inactive list. Also, like as the file LRU list,
> if enough reference happens, the page will be promoted. This simple
> modification changes the above example as following.
One wonders why on earth we weren't doing these things in the first
place?
> * SUBJECT
> workingset detection
It sounds like the above simple aging changes provide most of the
improvement, and that the workingset changes are less beneficial and a
bit more risky/speculative?
If so, would it be best for us to concentrate on the aging changes
first, let that settle in and spread out and then turn attention to the
workingset changes?
next prev parent reply other threads:[~2020-02-27 3:39 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-20 5:11 [PATCH v2 0/9] workingset protection/detection on the anonymous LRU list js1304
2020-02-20 5:11 ` [PATCH v2 1/9] mm/vmscan: make active/inactive ratio as 1:1 for anon lru js1304
2020-03-12 14:47 ` Johannes Weiner
2020-03-13 5:48 ` Joonsoo Kim
2020-02-20 5:11 ` [PATCH v2 2/9] mm/vmscan: protect the workingset on anonymous LRU js1304
2020-03-12 15:14 ` Johannes Weiner
2020-03-13 7:40 ` Joonsoo Kim
2020-03-13 19:55 ` Johannes Weiner
2020-03-16 7:05 ` Joonsoo Kim
2020-03-16 16:12 ` Johannes Weiner
2020-03-17 4:52 ` Joonsoo Kim
2020-02-20 5:11 ` [PATCH v2 3/9] mm/workingset: extend the workingset detection for anon LRU js1304
2020-02-20 5:11 ` [PATCH v2 4/9] mm/swapcache: support to handle the value in swapcache js1304
2020-02-20 5:11 ` [PATCH v2 5/9] mm/workingset: use the node counter if memcg is the root memcg js1304
2020-02-20 5:11 ` [PATCH v2 6/9] mm/workingset: handle the page without memcg js1304
2020-02-20 5:11 ` [PATCH v2 7/9] mm/swap: implement workingset detection for anonymous LRU js1304
2020-02-20 5:11 ` [PATCH v2 8/9] mm/vmscan: restore active/inactive ratio " js1304
2020-02-20 5:11 ` [PATCH v2 9/9] mm/swap: count a new anonymous page as a reclaim_state's rotate js1304
2020-02-27 3:39 ` Andrew Morton [this message]
2020-02-27 7:48 ` [PATCH v2 0/9] workingset protection/detection on the anonymous LRU list Joonsoo Kim
2020-03-01 4:40 ` Andrew Morton
2020-02-27 13:48 ` Johannes Weiner
2020-02-27 23:36 ` Andrew Morton
2020-03-02 23:31 ` Joonsoo Kim
2020-03-11 7:27 ` Joonsoo Kim
2020-02-28 3:23 ` Aaron Lu
2020-02-28 4:03 ` Joonsoo Kim
2020-02-28 5:57 ` Aaron Lu
2020-02-28 6:52 ` Joonsoo Kim
2020-02-28 9:17 ` Aaron Lu
2020-02-28 9:56 ` Joonsoo Kim
2020-02-28 10:21 ` Aaron Lu
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