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Message-ID: <13223d50-6218-49db-8356-700a1907e224@huawei.com>
Date: Tue, 10 Dec 2024 14:41:18 +0800
From: chenridong <chenridong@...wei.com>
To: Barry Song <21cnbao@...il.com>, Chen Ridong <chenridong@...weicloud.com>
CC: <akpm@...ux-foundation.org>, <mhocko@...e.com>, <hannes@...xchg.org>,
<yosryahmed@...gle.com>, <yuzhao@...gle.com>, <david@...hat.com>,
<willy@...radead.org>, <ryan.roberts@....com>, <wangkefeng.wang@...wei.com>,
<linux-mm@...ck.org>, <linux-kernel@...r.kernel.org>,
<wangweiyang2@...wei.com>, <xieym_ict@...mail.com>
Subject: Re: [PATCH v4 1/1] mm: vmascan: retry folios written back while
isolated for traditional LRU
On 2024/12/10 12:54, Barry Song wrote:
> On Mon, Dec 9, 2024 at 4:46 PM Chen Ridong <chenridong@...weicloud.com> wrote:
>>
>> From: Chen Ridong <chenridong@...wei.com>
>>
>> The commit 359a5e1416ca ("mm: multi-gen LRU: retry folios written back
>> while isolated") only fixed the issue for mglru. However, this issue
>> also exists in the traditional active/inactive LRU. This issue will be
>> worse if THP is split, which makes the list longer and needs longer time
>> to finish a batch of folios reclaim.
>>
>> This issue should be fixed in the same way for the traditional LRU.
>> Therefore, the common logic was extracted to the 'find_folios_written_back'
>> function firstly, which is then reused in the 'shrink_inactive_list'
>> function. Finally, retry reclaiming those folios that may have missed the
>> rotation for traditional LRU.
>
> let's drop the cover-letter and refine the changelog.
>
Will update.
>>
>> Signed-off-by: Chen Ridong <chenridong@...wei.com>
>> ---
>> include/linux/mmzone.h | 3 +-
>> mm/vmscan.c | 108 +++++++++++++++++++++++++++++------------
>> 2 files changed, 77 insertions(+), 34 deletions(-)
>>
>> diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
>> index b36124145a16..47c6e8c43dcd 100644
>> --- a/include/linux/mmzone.h
>> +++ b/include/linux/mmzone.h
>> @@ -391,6 +391,7 @@ struct page_vma_mapped_walk;
>>
>> #define LRU_GEN_MASK ((BIT(LRU_GEN_WIDTH) - 1) << LRU_GEN_PGOFF)
>> #define LRU_REFS_MASK ((BIT(LRU_REFS_WIDTH) - 1) << LRU_REFS_PGOFF)
>> +#define LRU_REFS_FLAGS (BIT(PG_referenced) | BIT(PG_workingset))
>>
>> #ifdef CONFIG_LRU_GEN
>>
>> @@ -406,8 +407,6 @@ enum {
>> NR_LRU_GEN_CAPS
>> };
>>
>> -#define LRU_REFS_FLAGS (BIT(PG_referenced) | BIT(PG_workingset))
>> -
>> #define MIN_LRU_BATCH BITS_PER_LONG
>> #define MAX_LRU_BATCH (MIN_LRU_BATCH * 64)
>>
>> diff --git a/mm/vmscan.c b/mm/vmscan.c
>> index 76378bc257e3..1f0d194f8b2f 100644
>> --- a/mm/vmscan.c
>> +++ b/mm/vmscan.c
>> @@ -283,6 +283,48 @@ static void set_task_reclaim_state(struct task_struct *task,
>> task->reclaim_state = rs;
>> }
>>
>> +/**
>> + * find_folios_written_back - Find and move the written back folios to a new list.
>> + * @list: filios list
>> + * @clean: the written back folios list
>> + * @skip: whether skip to move the written back folios to clean list.
>> + */
>> +static inline void find_folios_written_back(struct list_head *list,
>> + struct list_head *clean, bool skip)
>> +{
>> + struct folio *folio;
>> + struct folio *next;
>> +
>> + list_for_each_entry_safe_reverse(folio, next, list, lru) {
>> + if (!folio_evictable(folio)) {
>> + list_del(&folio->lru);
>> + folio_putback_lru(folio);
>> + continue;
>> + }
>> +
>> + if (folio_test_reclaim(folio) &&
>> + (folio_test_dirty(folio) || folio_test_writeback(folio))) {
>> + /* restore LRU_REFS_FLAGS cleared by isolate_folio() */
>> + if (lru_gen_enabled() && folio_test_workingset(folio))
>> + folio_set_referenced(folio);
>> + continue;
>> + }
>> +
>> + if (skip || folio_test_active(folio) || folio_test_referenced(folio) ||
>> + folio_mapped(folio) || folio_test_locked(folio) ||
>> + folio_test_dirty(folio) || folio_test_writeback(folio)) {
>> + /* don't add rejected folios to the oldest generation */
>> + if (lru_gen_enabled())
>> + set_mask_bits(&folio->flags, LRU_REFS_MASK | LRU_REFS_FLAGS,
>> + BIT(PG_active));
>> + continue;
>> + }
>> +
>> + /* retry folios that may have missed folio_rotate_reclaimable() */
>> + list_move(&folio->lru, clean);
>> + }
>> +}
>> +
>> /*
>> * flush_reclaim_state(): add pages reclaimed outside of LRU-based reclaim to
>> * scan_control->nr_reclaimed.
>> @@ -1907,6 +1949,25 @@ static int current_may_throttle(void)
>> return !(current->flags & PF_LOCAL_THROTTLE);
>> }
>>
>> +static inline void acc_reclaimed_stat(struct reclaim_stat *stat,
>> + struct reclaim_stat *curr)
>> +{
>> + int i;
>> +
>> + stat->nr_dirty += curr->nr_dirty;
>> + stat->nr_unqueued_dirty += curr->nr_unqueued_dirty;
>> + stat->nr_congested += curr->nr_congested;
>> + stat->nr_writeback += curr->nr_writeback;
>> + stat->nr_immediate += curr->nr_immediate;
>> + stat->nr_pageout += curr->nr_pageout;
>> + stat->nr_ref_keep += curr->nr_ref_keep;
>> + stat->nr_unmap_fail += curr->nr_unmap_fail;
>> + stat->nr_lazyfree_fail += curr->nr_lazyfree_fail;
>> + stat->nr_demoted += curr->nr_demoted;
>> + for (i = 0; i < ANON_AND_FILE; i++)
>> + stat->nr_activate[i] = curr->nr_activate[i];
>> +}
>
> you had no this before, what's the purpose of this？
>
We may call shrink_folio_list twice, and the 'stat curr' will reset in
the shrink_folio_list function. We should accumulate the stats as a
whole, which will then be used to calculate the cost and return it to
the caller.
Thanks,
Ridong
>> +
>> /*
>> * shrink_inactive_list() is a helper for shrink_node(). It returns the number
>> * of reclaimed pages
>> @@ -1916,14 +1977,16 @@ static unsigned long shrink_inactive_list(unsigned long nr_to_scan,
>> enum lru_list lru)
>> {
>> LIST_HEAD(folio_list);
>> + LIST_HEAD(clean_list);
>> unsigned long nr_scanned;
>> unsigned int nr_reclaimed = 0;
>> unsigned long nr_taken;
>> - struct reclaim_stat stat;
>> + struct reclaim_stat stat, curr;
>> bool file = is_file_lru(lru);
>> enum vm_event_item item;
>> struct pglist_data *pgdat = lruvec_pgdat(lruvec);
>> bool stalled = false;
>> + bool skip_retry = false;
>>
>> while (unlikely(too_many_isolated(pgdat, file, sc))) {
>> if (stalled)
>> @@ -1957,10 +2020,20 @@ static unsigned long shrink_inactive_list(unsigned long nr_to_scan,
>> if (nr_taken == 0)
>> return 0;
>>
>> - nr_reclaimed = shrink_folio_list(&folio_list, pgdat, sc, &stat, false);
>> + memset(&stat, 0, sizeof(stat));
>> +retry:
>> + nr_reclaimed += shrink_folio_list(&folio_list, pgdat, sc, &curr, false);
>> + find_folios_written_back(&folio_list, &clean_list, skip_retry);
>> + acc_reclaimed_stat(&stat, &curr);
>>
>> spin_lock_irq(&lruvec->lru_lock);
>> move_folios_to_lru(lruvec, &folio_list);
>> + if (!list_empty(&clean_list)) {
>> + list_splice_init(&clean_list, &folio_list);
>> + skip_retry = true;
>> + spin_unlock_irq(&lruvec->lru_lock);
>> + goto retry;
>> + }
>>
>> __mod_lruvec_state(lruvec, PGDEMOTE_KSWAPD + reclaimer_offset(),
>> stat.nr_demoted);
>> @@ -4567,8 +4640,6 @@ static int evict_folios(struct lruvec *lruvec, struct scan_control *sc, int swap
>> int reclaimed;
>> LIST_HEAD(list);
>> LIST_HEAD(clean);
>> - struct folio *folio;
>> - struct folio *next;
>> enum vm_event_item item;
>> struct reclaim_stat stat;
>> struct lru_gen_mm_walk *walk;
>> @@ -4597,34 +4668,7 @@ static int evict_folios(struct lruvec *lruvec, struct scan_control *sc, int swap
>> scanned, reclaimed, &stat, sc->priority,
>> type ? LRU_INACTIVE_FILE : LRU_INACTIVE_ANON);
>>
>> - list_for_each_entry_safe_reverse(folio, next, &list, lru) {
>> - if (!folio_evictable(folio)) {
>> - list_del(&folio->lru);
>> - folio_putback_lru(folio);
>> - continue;
>> - }
>> -
>> - if (folio_test_reclaim(folio) &&
>> - (folio_test_dirty(folio) || folio_test_writeback(folio))) {
>> - /* restore LRU_REFS_FLAGS cleared by isolate_folio() */
>> - if (folio_test_workingset(folio))
>> - folio_set_referenced(folio);
>> - continue;
>> - }
>> -
>> - if (skip_retry || folio_test_active(folio) || folio_test_referenced(folio) ||
>> - folio_mapped(folio) || folio_test_locked(folio) ||
>> - folio_test_dirty(folio) || folio_test_writeback(folio)) {
>> - /* don't add rejected folios to the oldest generation */
>> - set_mask_bits(&folio->flags, LRU_REFS_MASK | LRU_REFS_FLAGS,
>> - BIT(PG_active));
>> - continue;
>> - }
>> -
>> - /* retry folios that may have missed folio_rotate_reclaimable() */
>> - list_move(&folio->lru, &clean);
>> - }
>> -
>> + find_folios_written_back(&list, &clean, skip_retry);
>> spin_lock_irq(&lruvec->lru_lock);
>>
>> move_folios_to_lru(lruvec, &list);
>> --
>> 2.34.1
>>
>
> Thanks
> Barry
>
>>
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