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Message-ID: <02e73251-33ff-4632-9d2c-bc268f397202@vivo.com>
Date: Fri, 20 Oct 2023 11:59:33 +0800
From: zhiguojiang <justinjiang@...o.com>
To: David Hildenbrand <david@...hat.com>,
Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
linux-kernel@...r.kernel.org
Cc: opensource.kernel@...o.com
Subject: Re: [PATCH v2 1/2] mm:vmscan: the dirty folio in folio_list skip
unmap
在 2023/10/19 22:15, David Hildenbrand 写道:
> [你通常不会收到来自 david@...hat.com 的电子邮件。请访问
> https://aka.ms/LearnAboutSenderIdentification，以了解这一点为什么很重要]
>
> On 19.10.23 15:14, Zhiguo Jiang wrote:
>> In the shrink_folio_list() the sources of the file dirty folio include
>> two ways below:
>> 1. The dirty folio is from the incoming parameter folio_list,
>> which is the inactive file lru.
>> 2. The dirty folio is from the PTE dirty bit transferred by
>> the try_to_unmap().
>>
>> For the first source of the dirty folio, if the dirty folio does not
>> support pageout, the dirty folio can skip unmap in advance to reduce
>> recyling time.
>>
>> Signed-off-by: Zhiguo Jiang <justinjiang@...o.com>
>> ---
>>
>> Changelog:
>> v1->v2:
>> 1. Keep the original judgment flow.
>> 2. Add the interface of folio_check_pageout().
>> 3. The dirty folio which does not support pageout in inactive file lru
>> skip unmap in advance.
>>
>> mm/vmscan.c | 103 +++++++++++++++++++++++++++++++++-------------------
>> 1 file changed, 66 insertions(+), 37 deletions(-)
>>
>> diff --git a/mm/vmscan.c b/mm/vmscan.c
>> index a68d01fcc307..e067269275a5 100755
>> --- a/mm/vmscan.c
>> +++ b/mm/vmscan.c
>> @@ -925,6 +925,44 @@ static void folio_check_dirty_writeback(struct
>> folio *folio,
>> mapping->a_ops->is_dirty_writeback(folio, dirty,
>> writeback);
>> }
>>
>> +/* Check if a dirty folio can support pageout in the recyling process*/
>> +static bool folio_check_pageout(struct folio *folio,
>> + struct pglist_data *pgdat)
>> +{
>> + int ret = true;
>> +
>> + /*
>> + * Anonymous folios are not handled by flushers and must be
>> written
>> + * from reclaim context. Do not stall reclaim based on them.
>> + * MADV_FREE anonymous folios are put into inactive file list too.
>> + * They could be mistakenly treated as file lru. So further anon
>> + * test is needed.
>> + */
>> + if (!folio_is_file_lru(folio) ||
>> + (folio_test_anon(folio) && !folio_test_swapbacked(folio)))
>> + goto out;
>> +
>> + if (folio_test_dirty(folio) &&
>> + (!current_is_kswapd() ||
>> + !folio_test_reclaim(folio) ||
>> + !test_bit(PGDAT_DIRTY, &pgdat->flags))) {
>> + /*
>> + * Immediately reclaim when written back.
>> + * Similar in principle to folio_deactivate()
>> + * except we already have the folio isolated
>> + * and know it's dirty
>> + */
>> + node_stat_mod_folio(folio, NR_VMSCAN_IMMEDIATE,
>> + folio_nr_pages(folio));
>> + folio_set_reclaim(folio);
>> +
>> + ret = false;
>> + }
>> +
>> +out:
>> + return ret;
>> +}
>> +
>> static struct folio *alloc_demote_folio(struct folio *src,
>> unsigned long private)
>> {
>> @@ -1078,6 +1116,12 @@ static unsigned int shrink_folio_list(struct
>> list_head *folio_list,
>> if (dirty && !writeback)
>> stat->nr_unqueued_dirty += nr_pages;
>>
>> + /* If the dirty folio dose not support pageout,
>> + * the dirty folio can skip this recycling.
>> + */
>> + if (!folio_check_pageout(folio, pgdat))
>> + goto activate_locked;
>> +
>> /*
>> * Treat this folio as congested if folios are cycling
>> * through the LRU so quickly that the folios marked
>> @@ -1261,43 +1305,6 @@ static unsigned int shrink_folio_list(struct
>> list_head *folio_list,
>> enum ttu_flags flags = TTU_BATCH_FLUSH;
>> bool was_swapbacked =
>> folio_test_swapbacked(folio);
>>
>> - if (folio_test_dirty(folio)) {
>> - /*
>> - * Only kswapd can writeback filesystem
>> folios
>> - * to avoid risk of stack overflow. But
>> avoid
>> - * injecting inefficient single-folio
>> I/O into
>> - * flusher writeback as much as
>> possible: only
>> - * write folios when we've encountered
>> many
>> - * dirty folios, and when we've already
>> scanned
>> - * the rest of the LRU for clean folios
>> and see
>> - * the same dirty folios again (with
>> the reclaim
>> - * flag set).
>> - */
>> - if (folio_is_file_lru(folio) &&
>> - (!current_is_kswapd() ||
>> - !folio_test_reclaim(folio) ||
>> - !test_bit(PGDAT_DIRTY,
>> &pgdat->flags))) {
>> - /*
>> - * Immediately reclaim when
>> written back.
>> - * Similar in principle to
>> folio_deactivate()
>> - * except we already have the
>> folio isolated
>> - * and know it's dirty
>> - */
>> - node_stat_mod_folio(folio,
>> NR_VMSCAN_IMMEDIATE,
>> - nr_pages);
>> - folio_set_reclaim(folio);
>> -
>> - goto activate_locked;
>> - }
>> -
>> - if (references == FOLIOREF_RECLAIM_CLEAN)
>> - goto keep_locked;
>> - if (!may_enter_fs(folio, sc->gfp_mask))
>> - goto keep_locked;
>> - if (!sc->may_writepage)
>> - goto keep_locked;
>> - }
>> -
>> if (folio_test_pmd_mappable(folio))
>> flags |= TTU_SPLIT_HUGE_PMD;
>>
>> @@ -1323,6 +1330,28 @@ static unsigned int shrink_folio_list(struct
>> list_head *folio_list,
>>
>> mapping = folio_mapping(folio);
>> if (folio_test_dirty(folio)) {
>> + /*
>> + * Only kswapd can writeback filesystem folios
>> + * to avoid risk of stack overflow. But avoid
>> + * injecting inefficient single-folio I/O into
>> + * flusher writeback as much as possible: only
>> + * write folios when we've encountered many
>> + * dirty folios, and when we've already scanned
>> + * the rest of the LRU for clean folios and see
>> + * the same dirty folios again (with the reclaim
>> + * flag set).
>> + */
>> + if (folio_is_file_lru(folio) &&
>> + !folio_check_pageout(folio, pgdat))
>> + goto activate_locked;
>> +
>> + if (references == FOLIOREF_RECLAIM_CLEAN)
>> + goto keep_locked;
>> + if (!may_enter_fs(folio, sc->gfp_mask))
>> + goto keep_locked;
>> + if (!sc->may_writepage)
>> + goto keep_locked;
>> +
>> /*
>> * Folio is dirty. Flush the TLB if a writable
>> entry
>> * potentially exists to avoid CPU writes after
>> I/O
>
> I'm confused. Did you apply this on top of v1 by accident?
Hi,
According to my modified mm_vmscan_lru_shrink_inactive test tracelog, in
the 32 scanned inactive file pages, 20 were dirty, and the 20 dirty
pages were not reclamed, but they took 20us to perform try_to_unmap.
I think unreclaimed dirty folio in inactive file lru can skip to perform
try_to_unmap. Please help to continue review. Thanks.
kswapd0-99 ( 99) [005] ..... 687.793724:
mm_vmscan_lru_shrink_inactive: [Justin] nid 0 scan=32 isolate=32
reclamed=12 nr_dirty=20 nr_unqueued_dirty=20 nr_writeback=0
nr_congested=0 nr_immediate=0 nr_activate[0]=0 nr_activate[1]=20
nr_ref_keep=0 nr_unmap_fail=0 priority=2
file=RECLAIM_WB_FILE|RECLAIM_WB_ASYNC total=39 exe=0 reference_cost=5
reference_exe=0 unmap_cost=21 unmap_exe=0 dirty_unmap_cost=20
dirty_unmap_exe=0 pageout_cost=0 pageout_exe=0
>
> --
> Cheers,
>
> David / dhildenb
>
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