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Date: Fri, 10 Nov 2023 10:13:41 +0800
From: zhiguojiang <justinjiang@...o.com>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: linux-mm@...ck.org, linux-kernel@...r.kernel.org,
Johannes Weiner <hannes@...xchg.org>,
opensource.kernel@...o.com
Subject: Re: [PATCH v2 1/1] mm: ALLOC_HIGHATOMIC flag allocation issue
在 2023/11/10 1:49, Andrew Morton 写道:
> On Thu, 9 Nov 2023 15:31:33 +0800 Zhiguo Jiang <justinjiang@...o.com> wrote:
>
>> Add a new bool* argument to pass return flag instead of *alloc_flags
>> and add the related comments.
> Please retain (and update) the changelog with each version of a patch.
ok, supplement in v3 patch:
https://lore.kernel.org/all/20231110020840.1031-1-justinjiang@vivo.com/
>
> For reviewers (please), here's the v1 changelog:
>
> : In case of alloc_flags contain ALLOC_HIGHATOMIC and alloc order
> : is order1/2/3/10 in rmqueue(), if pages are alloced successfully
> : from pcplist cache, and move a free pageblock from the alloced
> : migratetype freelist to MIGRATE_HIGHATOMIC freelist, rather than
> : alloc from MIGRATE_HIGHATOMIC freelist firstly, so this will result
> : in an increasing number of pages on the MIGRATE_HIGHATOMIC freelist,
> : pages in other migratetype freelist are reduced and more likely to
> : allocation failure.
> :
> : Currently the sequence of ALLOC_HIGHATOMIC allocation is:
> : pcplist cache --> buddy (batch >> order) allocation migratetype
> : freelist --> buddy MIGRATE_HIGHATOMIC freelist --> buddy allocation
> : migratetype freelist.
> :
> : Due to the fact that requesting pages from the pcplist cache is faster
> : than buddy, the sequence of modifying the ALLOC_HIGHATOMIC allocation is:
> : pcplist --> buddy MIGRATE_HIGHATOMIC freelist --> buddy allocation
> : migrate freelist.
> :
> : This patch can solve the allocation failure of the Non-ALLOC_HIGHATOMIC
> : alloc_flag due to excessive pages reservations in MIGRATE_HIGHATOMIC
> : freelists.
>
>> --- a/mm/internal.h
>> +++ b/mm/internal.h
>> @@ -905,7 +905,6 @@ unsigned int reclaim_clean_pages_from_list(struct zone *zone,
>> #endif
>> #define ALLOC_HIGHATOMIC 0x200 /* Allows access to MIGRATE_HIGHATOMIC */
>> #define ALLOC_KSWAPD 0x800 /* allow waking of kswapd, __GFP_KSWAPD_RECLAIM set */
>> -#define ALLOC_PCPLIST 0x1000 /* Allocations from pcplist */
>>
>> /* Flags that allow allocations below the min watermark. */
>> #define ALLOC_RESERVES (ALLOC_NON_BLOCK|ALLOC_MIN_RESERVE|ALLOC_HIGHATOMIC|ALLOC_OOM)
>> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
>> index 67cec88164b1..3c84c3e3eeb0 100755
>> --- a/mm/page_alloc.c
>> +++ b/mm/page_alloc.c
>> @@ -2854,6 +2854,11 @@ struct page *__rmqueue_pcplist(struct zone *zone, unsigned int order,
>> int batch = nr_pcp_alloc(pcp, zone, order);
>> int alloced;
>>
>> + /*
>> + * If pcplist is empty and alloc_flags is with ALLOC_HIGHATOMIC,
>> + * it should alloc from buddy highatomic migrate freelist firstly
>> + * to ensure quick and successful allocation.
>> + */
>> if (alloc_flags & ALLOC_HIGHATOMIC)
>> goto out;
>>
>> @@ -2925,8 +2930,8 @@ __no_sanitize_memory
>> static inline
>> struct page *rmqueue(struct zone *preferred_zone,
>> struct zone *zone, unsigned int order,
>> - gfp_t gfp_flags, unsigned int *alloc_flags,
>> - int migratetype)
>> + gfp_t gfp_flags, unsigned int alloc_flags,
>> + int migratetype, bool *highatomc_allocation)
>> {
>> struct page *page;
>>
>> @@ -2938,19 +2943,33 @@ struct page *rmqueue(struct zone *preferred_zone,
>>
>> if (likely(pcp_allowed_order(order))) {
>> page = rmqueue_pcplist(preferred_zone, zone, order,
>> - migratetype, *alloc_flags);
>> - if (likely(page)) {
>> - *alloc_flags |= ALLOC_PCPLIST;
>> + migratetype, alloc_flags);
>> + if (likely(page))
>> goto out;
>> - }
>> }
>>
>> - page = rmqueue_buddy(preferred_zone, zone, order, *alloc_flags,
>> + page = rmqueue_buddy(preferred_zone, zone, order, alloc_flags,
>> migratetype);
>>
>> + /*
>> + * The high-order atomic allocation pageblock reserved conditions:
>> + *
>> + * If the high-order atomic allocation page is alloced from pcplist,
>> + * the highatomic pageblock does not need to be reserved, which can
>> + * void to migrate an increasing number of pages into buddy
>> + * MIGRATE_HIGHATOMIC freelist and lead to an increasing risk of
>> + * allocation failure on other buddy migrate freelists.
>> + *
>> + * If the high-order atomic allocation page is alloced from buddy
>> + * highatomic migrate freelist, regardless of whether the allocation
>> + * is successful or not, the highatomic pageblock can try to be
>> + * reserved.
>> + */
>> + if (unlikely(alloc_flags & ALLOC_HIGHATOMIC))
>> + *highatomc_allocation = true;
>> out:
>> /* Separate test+clear to avoid unnecessary atomics */
>> - if ((*alloc_flags & ALLOC_KSWAPD) &&
>> + if ((alloc_flags & ALLOC_KSWAPD) &&
>> unlikely(test_bit(ZONE_BOOSTED_WATERMARK, &zone->flags))) {
>> clear_bit(ZONE_BOOSTED_WATERMARK, &zone->flags);
>> wakeup_kswapd(zone, 0, 0, zone_idx(zone));
>> @@ -3218,6 +3237,7 @@ get_page_from_freelist(gfp_t gfp_mask, unsigned int order, int alloc_flags,
>> struct pglist_data *last_pgdat = NULL;
>> bool last_pgdat_dirty_ok = false;
>> bool no_fallback;
>> + bool highatomc_allocation = false;
>>
>> retry:
>> /*
>> @@ -3349,7 +3369,7 @@ get_page_from_freelist(gfp_t gfp_mask, unsigned int order, int alloc_flags,
>>
>> try_this_zone:
>> page = rmqueue(ac->preferred_zoneref->zone, zone, order,
>> - gfp_mask, &alloc_flags, ac->migratetype);
>> + gfp_mask, alloc_flags, ac->migratetype, &highatomc_allocation);
>> if (page) {
>> prep_new_page(page, order, gfp_mask, alloc_flags);
>>
>> @@ -3357,8 +3377,7 @@ get_page_from_freelist(gfp_t gfp_mask, unsigned int order, int alloc_flags,
>> * If this is a high-order atomic allocation then check
>> * if the pageblock should be reserved for the future
>> */
>> - if (unlikely(alloc_flags & ALLOC_HIGHATOMIC) &&
>> - unlikely(!(alloc_flags & ALLOC_PCPLIST)))
>> + if (unlikely(highatomc_allocation))
>> reserve_highatomic_pageblock(page, zone);
>>
>> return page;
>> --
>> 2.39.0
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