Re: [PATCH RFC] delayacct: add memory reclaim delay in get_page_from_freelist

["liwenyu01@bilibili.com" <liwenyu01@bilibili.com>]

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>> reclaim of the task in do_try_to_free_pages(). In systems with NUMA
>> open, some tasks occasionally experience slower response times, but the
>> total count of reclaim does not increase, using ftrace can show that
>> node_reclaim has occurred.
>>
>> The memory reclaim occurring in get_page_from_freelist() is also due to
>> heavy memory load. To get the impact of tasks in memory reclaim, this
>> patch adds the statistics of the memory reclaim delay statistics for
>> __node_reclaim().
>>
>> ...
>>
>> --- a/mm/vmscan.c
>> +++ b/mm/vmscan.c
>> @@ -8010,6 +8010,7 @@ static int __node_reclaim(struct pglist_data *pgdat, gfp_t gfp_mask, unsigned in
>>
>>         cond_resched();
>>         psi_memstall_enter(&pflags);
>> +       delayacct_freepages_start();
>>         fs_reclaim_acquire(sc.gfp_mask);
>>         /*
>>          * We need to be able to allocate from the reserves for RECLAIM_UNMAP
>> @@ -8032,6 +8033,7 @@ static int __node_reclaim(struct pglist_data *pgdat, gfp_t gfp_mask, unsigned in
>>         memalloc_noreclaim_restore(noreclaim_flag);
>>         fs_reclaim_release(sc.gfp_mask);
>>         psi_memstall_leave(&pflags);
>> +       delayacct_freepages_end();
>>
>>         trace_mm_vmscan_node_reclaim_end(sc.nr_reclaimed);
>
> __node_reclaim() calls shrink_node() which at some point will call
> do_try_to_free_pages() (yes?), which calls delayacct_freepages_start().
>
> So we're effectively nesting calls to delayacct_freepages_start(),
> which isn't designed for that?
>
sorry, the last reply was a mistake.

It seems that no point in shrink_node() will call do_try_to_free_pages().
And do_try_to_free_pages() will call shrink_node() through shrink_zones(),
if shrink_node() also has some point will call do_try_to_free_pages,then
delayacct_freepages_start() is nested now?

best wishes.


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