[lkml]   [2022]   [Dec]   [11]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: [PATCH 5/5] swap: avoid ra statistic lost when swapin races
Kairui Song <> writes:

> Matthew Wilcox <> 于2022年12月9日周五 03:14写道:
> Hi, thanks for the review.
>> On Fri, Dec 09, 2022 at 02:02:09AM +0800, Kairui Song wrote:
>> > From: Kairui Song <>
>> >
>> > __read_swap_cache_async should just call swap_cache_get_folio for trying
>> > to look up the swap cache. Because swap_cache_get_folio handles the
>> > readahead statistic, and clears the RA flag, looking up the cache
>> > directly will skip these parts.
>> >
>> > And the comment no longer applies after commit 442701e7058b
>> > ("mm/swap: remove swap_cache_info statistics"), just remove them.
>> But what about the readahead stats?
> Shouldn't readahead stats be accounted here? __read_swap_cache_async
> is called by swap read in path, if it hits the swap cache, and the
> page have readahead page flag set, then accounting that readahead
> should be just the right thing todo. And the readahead flag is checked
> with folio_test_clear_readahead, so there should be no issue about
> repeated accounting.
> Only the addr info of the swap_readahead_info could be updated for
> multiple times by racing readers, but I think that seems fine, since
> we don't know which swap read comes later in case of race, just let
> the last reader that hits the swap cache update the address info of
> readahead makes sense to me.
> Or do you mean I should update the comment about the readahead stat
> instead of just drop the commnet?

__read_swap_cache_async() is called by readahead too
(swap_vma_readahead/__read_swap_cache_async). I don't think that it's a
good idea to do swap readahead operation in this function.

Best Regards,
Huang, Ying

 \ /
  Last update: 2022-12-11 13:04    [W:0.049 / U:0.072 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site