linux-kernel - Re: [PATCH v2 1/2] mm:vmscan: the dirty folio in folio

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Date:   Tue, 24 Oct 2023 15:21:38 +0800
From:   zhiguojiang <justinjiang@...o.com>
To:     David Hildenbrand <david@...hat.com>,
        Matthew Wilcox <willy@...radead.org>
Cc:     Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, opensource.kernel@...o.com
Subject: Re: [PATCH v2 1/2] mm:vmscan: the dirty folio in folio_list skip
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在 2023/10/24 15:07, David Hildenbrand 写道:
> On 24.10.23 04:04, zhiguojiang wrote:
>>
>>
>> 在 2023/10/23 21:01, Matthew Wilcox 写道:
>>> On Mon, Oct 23, 2023 at 08:44:55PM +0800, zhiguojiang wrote:
>>>> 在 2023/10/23 20:21, Matthew Wilcox 写道:
>>>>> On Mon, Oct 23, 2023 at 04:07:28PM +0800, zhiguojiang wrote:
>>>>>>> Are you seeing measurable changes for any workloads?  It 
>>>>>>> certainly seems
>>>>>>> like you should, but it would help if you chose a test from 
>>>>>>> mmtests and
>>>>>>> showed how performance changed on your system.
>>>>>> In one mmtest, the max times for a invalid recyling of a 
>>>>>> folio_list dirty
>>>>>> folio that does not support pageout and has been activated in
>>>>>> shrink_folio_list() are: cost=51us, exe=2365us.
>>>>>>
>>>>>> Calculate according to this formula: dirty_cost / total_cost * 
>>>>>> 100%, the
>>>>>> recyling efficiency of dirty folios can be improved 53.13%、82.95%.
>>>>>>
>>>>>> So this patch can optimize shrink efficiency and reduce the 
>>>>>> workload of
>>>>>> kswapd to a certain extent.
>>>>>>
>>>>>> kswapd0-96      (     96) [005] .....   387.218548:
>>>>>> mm_vmscan_lru_shrink_inactive: [Justin] nid 0 nr_scanned 32 
>>>>>> nr_taken 32
>>>>>> nr_reclaimed 31 nr_dirty  1 nr_unqueued_dirty  1 nr_writeback 0
>>>>>> nr_activate[1]  1 nr_ref_keep  0 f RECLAIM_WB_FILE|RECLAIM_WB_ASYNC
>>>>>> total_cost 96 total_exe 2365 dirty_cost 51 total_exe 2365
>>>>>>
>>>>>> kswapd0-96      (     96) [006] .....   412.822532:
>>>>>> mm_vmscan_lru_shrink_inactive: [Justin] nid 0 nr_scanned 32 
>>>>>> nr_taken 32
>>>>>> nr_reclaimed  0 nr_dirty 32 nr_unqueued_dirty 32 nr_writeback 0
>>>>>> nr_activate[1] 19 nr_ref_keep 13 f RECLAIM_WB_FILE|RECLAIM_WB_ASYNC
>>>>>> total_cost 88 total_exe 605  dirty_cost 73 total_exe 605
>>>>> I appreciate that you can put probes in and determine the cost, 
>>>>> but do
>>>>> you see improvements for a real workload?  Like doing a kernel 
>>>>> compile
>>>>> -- does it speed up at all?
>>>> Can you help share a method for testing thread workload, like kswapd?
>>> Something dirt simple like 'time make -j8'.
>> Two compilations were conducted separately, and compared to the
>> unmodified compilation,
>> the compilation time for adding modified patches had a certain
>> reduction, as follows:
>>
>> Compilation command:
>> make distclean -j8
>> make ARCH=x86_64 x86_64_defconfig
>> time make -j8
>>
>> 1.Unmodified Compilation time:
>> real    2m40.276s
>> user    16m2.956s
>> sys     2m14.738s
>>
>> real    2m40.136s
>> user    16m2.617s
>> sys     2m14.722s
>>
>> 2.[Patch v2 1/2] Modified Compilation time:
>> real    2m40.067s
>> user    16m3.164s
>> sys     2m14.211s
>>
>> real    2m40.123s
>> user    16m2.439s
>> sys     2m14.508s
>>
>> 3 [Patch v2 1/2] + [Patch v2 2/2] Modified Compilation time:
>> real    2m40.367s
>> user    16m3.738s
>> sys     2m13.662s
>>
>> real    2m40.014s
>> user    16m3.108s
>> sys     2m14.096s
>>
>
> To get expressive numbers two iterations are usually not sufficient. 
> How much memory does you system have? Does vmscan even ever get active?
Test system memory:  MemTotal:    8161608 kB.  When multiple Apps were 
opened, vmscan can get active. I can capture a lot of tracelog data 
through testing, I only posted two sets of tracelog data.