linux-kernel - Re: [PATCH 0/2] Support kshrinkd

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Message-ID: <a642d9dc-6d48-016c-7007-c08ce8933d18@oppo.com>
Date: Tue, 20 Feb 2024 10:04:33 +0800
From: 李培锋 <lipeifeng@...o.com>
To: Matthew Wilcox <willy@...radead.org>
Cc: akpm@...ux-foundation.org, david@...hat.com, osalvador@...e.de,
 linux-mm@...ck.org, linux-kernel@...r.kernel.org, v-songbaohua@...o.com,
 gregkh@...gle.com, tkjos@...gle.com
Subject: Re: [PATCH 0/2] Support kshrinkd


在 2024/2/20 0:51, Matthew Wilcox 写道:
> On Mon, Feb 19, 2024 at 10:17:01PM +0800, lipeifeng@...o.com wrote:
>> 'commit 6d4675e60135 ("mm: don't be stuck to rmap lock on reclaim path")'
>> The above patch would avoid reclaim path to stuck rmap lock.
>> But it would cause some folios in LRU not sorted by aging because
>> the contended-folios in rmap_walk would be putbacked to the head of LRU
>> during shrink_folio_list even if the folios are very cold.
>>
>> The patchset setups new kthread:kshrinkd to reclaim the contended-folio
>> in rmap_walk when shrink_folio_list, to avoid to break the rules of LRU.
> Patch 1/2 didn't make it to my inbox or to lore.
Hi Sir, I had resent to you.
>   But you should talk
> about the real world consequences of this in the cover letter.  What do
> we observe if this problem happens?  How much extra performance will we
> gain by applying this patch?

Hi Sir:

Monkey-test in phone with 16G-ram for 300 hours shows that almost one-third

of the contended-pages can be freed successfully next time, putting back 
those

folios to LRU's head would break the rules of inative-LRU.

- pgsteal_kshrinkd 262577
- pgscan_kshrinkd 795503


"pgsteal_kshrinkd" means that the amount of those contended-folios which 
can be

freed successfully but be putbacked in the head of inactive-LRU, more 
than 1GB(262577 folios).

Mobile-phone with 16-ram, the total amount of inactive are around 4.5G, 
so that the

contended-folios would break the rules of inactive-LRU.

- nr_inactive_anon 1020953
- nr_inactive_file 204801


Actually, The patchset had been merged in Google kernel/common since

android12-5.10 and android13-5.15, and were taken in more than 100 millions

android-phone devices more than 1.5 years.

But for the reason of GKI, the patches were implemented in the form of 
hooks,

the patches merged in google-line as follows:

https://android-review.googlesource.com/c/kernel/common/+/2163904

https://android-review.googlesource.com/c/kernel/common/+/2191343

https://android-review.googlesource.com/c/kernel/common/+/2550490

https://android-review.googlesource.com/c/kernel/common/+/2318311