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From: Alexander Duyck <alexander.duyck@gmail.com>
To: Alex Shi <alex.shi@linux.alibaba.com>
Cc: Yang Shi <yang.shi@linux.alibaba.com>,
	kbuild test robot <lkp@intel.com>,
	 Rong Chen <rong.a.chen@intel.com>,
	Konstantin Khlebnikov <khlebnikov@yandex-team.ru>,
	 "Kirill A. Shutemov" <kirill@shutemov.name>,
	Hugh Dickins <hughd@google.com>,
	 LKML <linux-kernel@vger.kernel.org>,
	Daniel Jordan <daniel.m.jordan@oracle.com>,
	 linux-mm <linux-mm@kvack.org>,
	Shakeel Butt <shakeelb@google.com>,
	 Matthew Wilcox <willy@infradead.org>,
	Johannes Weiner <hannes@cmpxchg.org>, Tejun Heo <tj@kernel.org>,
	 cgroups@vger.kernel.org,
	Andrew Morton <akpm@linux-foundation.org>,
	 Wei Yang <richard.weiyang@gmail.com>,
	Mel Gorman <mgorman@techsingularity.net>,
	 Joonsoo Kim <iamjoonsoo.kim@lge.com>
Subject: Re: [RFC PATCH 2/3] mm: Drop use of test_and_set_skip in favor of just setting skip
Date: Mon, 17 Aug 2020 08:38:02 -0700
Message-ID: <CAKgT0Ud5D3vAtC0_+3otdqzm+hfqR9xGBacjpuh5Qze5=J1=Vw@mail.gmail.com> (raw)
In-Reply-To: <650ab639-e66f-5ca6-a9a5-31e61c134ae7@linux.alibaba.com>

On Sat, Aug 15, 2020 at 2:51 AM Alex Shi <alex.shi@linux.alibaba.com> wrote:
>
>
>
> 在 2020/8/15 上午5:15, Alexander Duyck 写道:
> > On Fri, Aug 14, 2020 at 7:24 AM Alexander Duyck
> > <alexander.duyck@gmail.com> wrote:
> >>
> >> On Fri, Aug 14, 2020 at 12:19 AM Alex Shi <alex.shi@linux.alibaba.com> wrote:
> >>>
> >>>
> >>>
> >>> 在 2020/8/13 下午12:02, Alexander Duyck 写道:
> >>>>
> >>>> Since we have dropped the late abort case we can drop the code that was
> >>>> clearing the LRU flag and calling page_put since the abort case will now
> >>>> not be holding a reference to a page.
> >>>>
> >>>> Signed-off-by: Alexander Duyck <alexander.h.duyck@linux.intel.com>
> >>>
> >>> seems the case-lru-file-mmap-read case drop about 3% on this patch in a rough testing.
> >>> on my 80 core machine.
> >>
> >> I'm not sure how it could have that much impact on the performance
> >> since the total effect would just be dropping what should be a
> >> redundant test since we tested the skip bit before we took the LRU
> >> bit, so we shouldn't need to test it again after.
> >>
> >> I finally got my test setup working last night. I'll have to do some
> >> testing in my environment and I can start trying to see what is going
> >> on.
> >
> > So I ran the case-lru-file-mmap-read a few times and I don't see how
> > it is supposed to be testing the compaction code. It doesn't seem like
> > compaction is running at least on my system as a result of the test
> > script.
>
> atteched my kernel config, it is used on mine machine,

I'm just wondering what the margin of error is on the tests you are
running. What is the variance between runs? I'm just wondering if 3%
falls into the range of noise or possible changes due to just code
shifting around?

In order for the code to have shown any change it needs to be run and
I didn't see the tests triggering compaction on my test system. I'm
wondering how much memory you have available in the system you were
testing on that the test was enough to trigger compaction?

> > I wonder if testing this code wouldn't be better done using
> > something like thpscale from the
> > mmtests(https://github.com/gormanm/mmtests)? It seems past changes to
> > the compaction code were tested using that, and the config script for
> > the test explains that it is designed specifically to stress the
> > compaction code. I have the test up and running now and hope to
> > collect results over the weekend.
>
> I did the testing, but a awkward is that I failed to get result,
> maybe leak some packages.

So one thing I noticed is that if you have over 128GB of memory in the
system it will fail unless you update the sysctl value
vm.max_map_count. It defaulted to somewhere close to 64K, and I
increased it 20X to 1280K in order for the test to run without failing
on the mmap calls. The other edit I had to make was the config file as
the test system I was on had about 1TB of RAM, and my home partition
only had about 800GB to spare so I had to reduce the map size from
8/10 to 5/8.

> # ../../compare-kernels.sh
>
> thpscale Fault Latencies
> Can't locate List/BinarySearch.pm in @INC (@INC contains: /root/mmtests/bin/lib /usr/local/lib64/perl5 /usr/local/share/perl5 /usr/lib64/perl5/vendor_perl /usr/share/perl5/vend.
> BEGIN failed--compilation aborted at /root/mmtests/bin/lib/MMTests/Stat.pm line 13.
> Compilation failed in require at /root/mmtests/work/log/../../bin/compare-mmtests.pl line 13.
> BEGIN failed--compilation aborted at /root/mmtests/work/log/../../bin/compare-mmtests.pl line 13.

I had to install List::BinarySearch.pm. It required installing the
cpan perl libraries.

> >
> > There is one change I will probably make to this patch and that is to
> > place the new code that is setting skip_updated where the old code was
> > calling test_and_set_skip_bit. By doing that we can avoid extra checks
> > and it should help to reduce possible collisions when setting the skip
> > bit in the pageblock flags.
>
> the problem maybe on cmpchxg pb flags, that may involved other blocks changes.

That is the only thing I can think of just based on code review.
Although that would imply multiple compact threads are running, and as
I said in my tests I never saw kcompactd wakeup so I don't think the
tests you were mentioning were enough to stress compaction.


  reply index

Thread overview: 102+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-25 12:59 [PATCH v17 00/21] per memcg lru lock Alex Shi
2020-07-25 12:59 ` [PATCH v17 01/21] mm/vmscan: remove unnecessary lruvec adding Alex Shi
2020-08-06  3:47   ` Alex Shi
2020-07-25 12:59 ` [PATCH v17 02/21] mm/page_idle: no unlikely double check for idle page counting Alex Shi
2020-07-25 12:59 ` [PATCH v17 03/21] mm/compaction: correct the comments of compact_defer_shift Alex Shi
2020-07-27 17:29   ` Alexander Duyck
2020-07-28 11:59     ` Alex Shi
2020-07-28 14:17       ` Alexander Duyck
2020-07-25 12:59 ` [PATCH v17 04/21] mm/compaction: rename compact_deferred as compact_should_defer Alex Shi
2020-07-25 12:59 ` [PATCH v17 05/21] mm/thp: move lru_add_page_tail func to huge_memory.c Alex Shi
2020-07-25 12:59 ` [PATCH v17 06/21] mm/thp: clean up lru_add_page_tail Alex Shi
2020-07-25 12:59 ` [PATCH v17 07/21] mm/thp: remove code path which never got into Alex Shi
2020-07-25 12:59 ` [PATCH v17 08/21] mm/thp: narrow lru locking Alex Shi
2020-07-25 12:59 ` [PATCH v17 09/21] mm/memcg: add debug checking in lock_page_memcg Alex Shi
2020-07-25 12:59 ` [PATCH v17 10/21] mm/swap: fold vm event PGROTATED into pagevec_move_tail_fn Alex Shi
2020-07-25 12:59 ` [PATCH v17 11/21] mm/lru: move lru_lock holding in func lru_note_cost_page Alex Shi
2020-08-05 21:18   ` Alexander Duyck
2020-07-25 12:59 ` [PATCH v17 12/21] mm/lru: move lock into lru_note_cost Alex Shi
2020-07-25 12:59 ` [PATCH v17 13/21] mm/lru: introduce TestClearPageLRU Alex Shi
2020-07-29  3:53   ` Alex Shi
2020-08-05 22:43     ` Alexander Duyck
2020-08-06  1:54       ` Alex Shi
2020-08-06 14:41         ` Alexander Duyck
2020-07-25 12:59 ` [PATCH v17 14/21] mm/compaction: do page isolation first in compaction Alex Shi
2020-08-04 21:35   ` Alexander Duyck
2020-08-06 18:38   ` Alexander Duyck
2020-08-07  3:24     ` Alex Shi
2020-08-07 14:51       ` Alexander Duyck
2020-08-10 13:10         ` Alex Shi
2020-08-10 14:41           ` Alexander Duyck
2020-08-11  8:22             ` Alex Shi
2020-08-11 14:47               ` Alexander Duyck
2020-08-12 11:43                 ` Alex Shi
2020-08-12 12:16                   ` Alex Shi
2020-08-12 16:51                   ` Alexander Duyck
2020-08-13  1:46                     ` Alex Shi
2020-08-13  2:17                       ` Alexander Duyck
2020-08-13  3:52                         ` Alex Shi
2020-08-13  4:02                       ` [RFC PATCH 0/3] " Alexander Duyck
2020-08-13  4:02                         ` [RFC PATCH 1/3] mm: Drop locked from isolate_migratepages_block Alexander Duyck
2020-08-13  6:56                           ` Alex Shi
2020-08-13 14:32                             ` Alexander Duyck
2020-08-14  7:25                               ` Alex Shi
2020-08-13  7:44                           ` Alex Shi
2020-08-13 14:26                             ` Alexander Duyck
2020-08-13  4:02                         ` [RFC PATCH 2/3] mm: Drop use of test_and_set_skip in favor of just setting skip Alexander Duyck
2020-08-14  7:19                           ` Alex Shi
2020-08-14 14:24                             ` Alexander Duyck
2020-08-14 21:15                               ` Alexander Duyck
2020-08-15  9:49                                 ` Alex Shi
2020-08-17 15:38                                   ` Alexander Duyck [this message]
2020-08-18  6:50                           ` Alex Shi
2020-08-13  4:02                         ` [RFC PATCH 3/3] mm: Identify compound pages sooner in isolate_migratepages_block Alexander Duyck
2020-08-14  7:20                           ` Alex Shi
2020-08-17 22:58   ` [PATCH v17 14/21] mm/compaction: do page isolation first in compaction Alexander Duyck
2020-07-25 12:59 ` [PATCH v17 15/21] mm/thp: add tail pages into lru anyway in split_huge_page() Alex Shi
2020-07-25 12:59 ` [PATCH v17 16/21] mm/swap: serialize memcg changes in pagevec_lru_move_fn Alex Shi
2020-07-25 12:59 ` [PATCH v17 17/21] mm/lru: replace pgdat lru_lock with lruvec lock Alex Shi
2020-07-27 23:34   ` Alexander Duyck
2020-07-28  7:15     ` Alex Shi
2020-07-28 11:19     ` Alex Shi
2020-07-28 14:54       ` Alexander Duyck
2020-07-29  1:00         ` Alex Shi
2020-07-29  1:27           ` Alexander Duyck
2020-07-29  2:27             ` Alex Shi
2020-07-28 15:39     ` Alex Shi
2020-07-28 15:55       ` Alexander Duyck
2020-07-29  0:48         ` Alex Shi
2020-07-29  3:54   ` Alex Shi
2020-08-06  7:41   ` Alex Shi
2020-07-25 12:59 ` [PATCH v17 18/21] mm/lru: introduce the relock_page_lruvec function Alex Shi
2020-07-29 17:52   ` Alexander Duyck
2020-07-30  6:08     ` Alex Shi
2020-07-31 14:20       ` Alexander Duyck
2020-07-31 21:14   ` [PATCH RFC] mm: Add function for testing if the current lruvec lock is valid alexander.h.duyck
2020-07-31 23:54     ` Alex Shi
2020-08-02 18:20       ` Alexander Duyck
2020-08-04  6:13         ` Alex Shi
2020-07-25 12:59 ` [PATCH v17 19/21] mm/vmscan: use relock for move_pages_to_lru Alex Shi
2020-08-03 22:49   ` Alexander Duyck
2020-08-04  6:23     ` Alex Shi
2020-07-25 12:59 ` [PATCH v17 20/21] mm/pgdat: remove pgdat lru_lock Alex Shi
2020-08-03 22:42   ` Alexander Duyck
2020-08-03 22:45     ` Alexander Duyck
2020-08-04  6:22       ` Alex Shi
2020-07-25 12:59 ` [PATCH v17 21/21] mm/lru: revise the comments of lru_lock Alex Shi
2020-08-03 22:37   ` Alexander Duyck
2020-08-04 10:04     ` Alex Shi
2020-08-04 14:29       ` Alexander Duyck
2020-08-06  1:39         ` Alex Shi
2020-08-06 16:27           ` Alexander Duyck
2020-07-27  5:40 ` [PATCH v17 00/21] per memcg lru lock Alex Shi
2020-07-29 14:49   ` Alex Shi
2020-07-29 18:06     ` Hugh Dickins
2020-07-30  2:16       ` Alex Shi
2020-08-03 15:07         ` Michal Hocko
2020-08-04  6:14           ` Alex Shi
2020-07-31 21:31 ` Alexander Duyck
2020-08-04  8:36 ` Alex Shi
2020-08-04  8:36 ` Alex Shi
2020-08-04  8:37 ` Alex Shi
2020-08-04  8:37 ` Alex Shi

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