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Message-ID: <c3932a6f-77fe-29f7-0c29-fe6b1c67ab7b@gmail.com>
Date: Thu, 26 May 2022 12:46:44 -0700
From: Doug Berger <opendmb@...il.com>
To: Zi Yan <ziy@...dia.com>
Cc: David Hildenbrand <david@...hat.com>, linux-mm@...ck.org,
linux-kernel@...r.kernel.org,
virtualization@...ts.linux-foundation.org,
Vlastimil Babka <vbabka@...e.cz>,
Mel Gorman <mgorman@...hsingularity.net>,
Eric Ren <renzhengeek@...il.com>,
Mike Rapoport <rppt@...nel.org>,
Oscar Salvador <osalvador@...e.de>,
Christophe Leroy <christophe.leroy@...roup.eu>,
Andrew Morton <akpm@...ux-foundation.org>,
kernel test robot <lkp@...el.com>,
Qian Cai <quic_qiancai@...cinc.com>
Subject: Re: [PATCH v11 3/6] mm: make alloc_contig_range work at pageblock
granularity
On 5/26/2022 10:34 AM, Zi Yan wrote:
> On 25 May 2022, at 17:11, Zi Yan wrote:
>
>> On 25 May 2022, at 17:03, Doug Berger wrote:
>>
>>> On 5/25/2022 10:53 AM, Zi Yan wrote:
>>>> On 25 May 2022, at 13:41, Doug Berger wrote:
>>>>
>>>>> I am seeing some free memory accounting problems with linux-next that I have bisected to this commit (i.e. b2c9e2fbba32 ("mm: make alloc_contig_range work at pageblock granularity").
>>>>>
>>>>> On an arm64 SMP platform with 4GB total memory and the default 16MB default CMA pool, I am seeing the following after boot with a sysrq Show Memory (e.g. 'echo m > /proc/sysrq-trigger'):
>>>>>
>>>>> [ 16.015906] sysrq: Show Memory
>>>>> [ 16.019039] Mem-Info:
>>>>> [ 16.021348] active_anon:14604 inactive_anon:919 isolated_anon:0
>>>>> [ 16.021348] active_file:0 inactive_file:0 isolated_file:0
>>>>> [ 16.021348] unevictable:0 dirty:0 writeback:0
>>>>> [ 16.021348] slab_reclaimable:3662 slab_unreclaimable:3333
>>>>> [ 16.021348] mapped:928 shmem:15146 pagetables:63 bounce:0
>>>>> [ 16.021348] kernel_misc_reclaimable:0
>>>>> [ 16.021348] free:976766 free_pcp:991 free_cma:7017
>>>>> [ 16.056937] Node 0 active_anon:58416kB inactive_anon:3676kB active_file:0kB inactive_file:0kB unevictable:0kB isolated(anon):0kB isolated(file):0kB mapped:3712kB dirty:0kB writeback:0kB shmem:60584kB writeback_tmp:0kB kernel_stack:1200kB pagetables:252kB all_unreclaimable? no
>>>>> [ 16.081526] DMA free:3041036kB boost:0kB min:6036kB low:9044kB high:12052kB reserved_highatomic:0KB active_anon:0kB inactive_anon:0kB active_file:0kB inactive_file:0kB unevictable:0kB writepending:0kB present:3145728kB managed:3029992kB mlocked:0kB bounce:0kB free_pcp:636kB local_pcp:0kB free_cma:28068kB
>>>>> [ 16.108650] lowmem_reserve[]: 0 0 944 944
>>>>> [ 16.112746] Normal free:866028kB boost:0kB min:1936kB low:2900kB high:3864kB reserved_highatomic:0KB active_anon:58416kB inactive_anon:3676kB active_file:0kB inactive_file:0kB unevictable:0kB writepending:0kB present:1048576kB managed:967352kB mlocked:0kB bounce:0kB free_pcp:3328kB local_pcp:864kB free_cma:0kB
>>>>> [ 16.140393] lowmem_reserve[]: 0 0 0 0
>>>>> [ 16.144133] DMA: 7*4kB (UMC) 4*8kB (M) 3*16kB (M) 3*32kB (MC) 5*64kB (M) 4*128kB (MC) 5*256kB (UMC) 7*512kB (UM) 5*1024kB (UM) 9*2048kB (UMC) 732*4096kB (MC) = 3027724kB
>>>>> [ 16.159609] Normal: 149*4kB (UM) 95*8kB (UME) 26*16kB (UME) 8*32kB (ME) 2*64kB (UE) 1*128kB (M) 2*256kB (ME) 2*512kB (ME) 2*1024kB (UM) 0*2048kB 210*4096kB (M) = 866028kB
>>>>> [ 16.175165] Node 0 hugepages_total=0 hugepages_free=0 hugepages_surp=0 hugepages_size=1048576kB
>>>>> [ 16.183937] Node 0 hugepages_total=0 hugepages_free=0 hugepages_surp=0 hugepages_size=32768kB
>>>>> [ 16.192533] Node 0 hugepages_total=0 hugepages_free=0 hugepages_surp=0 hugepages_size=2048kB
>>>>> [ 16.201040] Node 0 hugepages_total=0 hugepages_free=0 hugepages_surp=0 hugepages_size=64kB
>>>>> [ 16.209374] 15146 total pagecache pages
>>>>> [ 16.213246] 0 pages in swap cache
>>>>> [ 16.216595] Swap cache stats: add 0, delete 0, find 0/0
>>>>> [ 16.221867] Free swap = 0kB
>>>>> [ 16.224780] Total swap = 0kB
>>>>> [ 16.227693] 1048576 pages RAM
>>>>> [ 16.230694] 0 pages HighMem/MovableOnly
>>>>> [ 16.234564] 49240 pages reserved
>>>>> [ 16.237825] 4096 pages cma reserved
>>>>>
>>>>> Some anomolies in the above are:
>>>>> free_cma:7017 with only 4096 pages cma reserved
>>>>> DMA free:3041036kB with only managed:3029992kB
>>>>>
>>>>> I'm not sure what is going on here, but I am suspicious of split_free_page() since del_page_from_free_list doesn't affect migrate_type accounting, but __free_one_page() can.
>>>>> Also PageBuddy(page) is being checked without zone->lock in isolate_single_pageblock().
>>>>>
>>>>> Please investigate this as well.
>>>>
>>>>
>>>> Can you try this patch https://lore.kernel.org/linux-mm/20220524194756.1698351-1-zi.yan@sent.com/
>>>> and see if it fixes the issue?
>>>>
>>>> Thanks.
>>>>
>>> The last hunk didn't apply directly to this commit, but I was able to apply the patch to linux-next/master with no improvement to the free memory accounting (actually anecdotaly worse):
>>>
>>> [ 6.236828] sysrq: Show Memory
>>> [ 6.239973] Mem-Info:
>>> [ 6.242290] active_anon:14594 inactive_anon:924 isolated_anon:0
>>> [ 6.242290] active_file:0 inactive_file:0 isolated_file:0
>>> [ 6.242290] unevictable:0 dirty:0 writeback:0
>>> [ 6.242290] slab_reclaimable:3671 slab_unreclaimable:3575
>>> [ 6.242290] mapped:935 shmem:15147 pagetables:63 bounce:0
>>> [ 6.242290] kernel_misc_reclaimable:0
>>> [ 6.242290] free:1059009 free_pcp:1067 free_cma:90112
>>> [ 6.278048] Node 0 active_anon:58376kB inactive_anon:3844kB active_file:0kB inactive_file:0kB unevictable:0kB isolated(anon):0kB isolated(file):0kB mapped:3740kB dirty:0kB writeback:0kB shmem:60588kB writeback_tmp:0kB kernel_stack:1216kB pagetables:252kB all_unreclaimable? no
>>> [ 6.279422] arm-scmi brcm_scmi@0: timed out in resp(caller: scmi_perf_level_set+0xe0/0x110)
>>> [ 6.302501] DMA free:3372200kB boost:0kB min:6032kB low:9040kB high:12048kB reserved_highatomic:0KB active_anon:0kB inactive_anon:0kB active_file:0kB inactive_file:0kB unevictable:0kB writepending:0kB present:3145728kB managed:3029800kB mlocked:0kB bounce:0kB free_pcp:636kB local_pcp:0kB free_cma:360448kB
>>> [ 6.302515] lowmem_reserve[]: 0 0 944
>>> [ 6.310894] cpufreq: __target_index: Failed to change cpu frequency: -110
>>> [ 6.337920] 944
>>> [ 6.337925] Normal free:863584kB boost:0kB min:1940kB low:2904kB high:3868kB reserved_highatomic:0KB active_anon:58376kB inactive_anon:3896kB active_file:0kB inactive_file:0kB unevictable:0kB writepending:0kB present:1048576kB managed:967352kB mlocked:0kB bounce:0kB free_pcp:3492kB local_pcp:828kB free_cma:0kB
>>> [ 6.377782] lowmem_reserve[]: 0 0 0 0
>>> [ 6.381461] DMA: 4*4kB (UM) 5*8kB (M) 3*16kB (M) 2*32kB (M) 6*64kB (M) 5*128kB (M) 6*256kB (UM) 5*512kB (UM) 4*1024kB (M) 10*2048kB (UMC) 732*4096kB (MC) = 3028136kB
>>> [ 6.396324] Normal: 84*4kB (U) 94*8kB (UM) 260*16kB (UME) 149*32kB (UM) 99*64kB (UME) 39*128kB (UM) 12*256kB (U) 3*512kB (UME) 2*1024kB (UM) 0*2048kB 204*4096kB (M) = 863584kB
>>> [ 6.412054] Node 0 hugepages_total=0 hugepages_free=0 hugepages_surp=0 hugepages_size=1048576kB
>>> [ 6.420770] Node 0 hugepages_total=0 hugepages_free=0 hugepages_surp=0 hugepages_size=32768kB
>>> [ 6.429312] Node 0 hugepages_total=0 hugepages_free=0 hugepages_surp=0 hugepages_size=2048kB
>>> [ 6.437767] Node 0 hugepages_total=0 hugepages_free=0 hugepages_surp=0 hugepages_size=64kB
>>> [ 6.446047] 15147 total pagecache pages
>>> [ 6.449890] 0 pages in swap cache
>>> [ 6.453210] Swap cache stats: add 0, delete 0, find 0/0
>>> [ 6.458445] Free swap = 0kB
>>> [ 6.461331] Total swap = 0kB
>>> [ 6.464217] 1048576 pages RAM
>>> [ 6.467190] 0 pages HighMem/MovableOnly
>>> [ 6.471032] 49288 pages reserved
>>> [ 6.474267] 4096 pages cma reserved
>>>
>>> Regards,
>>> Doug
>>
>> I will look into it. Thanks for reporting it.
>
> Hi Doug,
>
> Can you try the patch below? It takes out free pages under zone lock now
> and modifies page stats properly. Thanks.
>
>
> diff --git a/mm/internal.h b/mm/internal.h
> index 64e61b032dac..c0f8fbe0445b 100644
> --- a/mm/internal.h
> +++ b/mm/internal.h
> @@ -374,8 +374,8 @@ extern void *memmap_alloc(phys_addr_t size, phys_addr_t align,
> phys_addr_t min_addr,
> int nid, bool exact_nid);
>
> -void split_free_page(struct page *free_page,
> - int order, unsigned long split_pfn_offset);
> +int split_free_page(struct page *free_page,
> + unsigned int order, unsigned long split_pfn_offset);
>
> #if defined CONFIG_COMPACTION || defined CONFIG_CMA
>
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index bc93a82e51e6..6f6e4649ac21 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -1100,30 +1100,44 @@ static inline void __free_one_page(struct page *page,
> * @order: the order of the page
> * @split_pfn_offset: split offset within the page
> *
> + * Return -ENOENT if the free page is changed, otherwise 0
> + *
> * It is used when the free page crosses two pageblocks with different migratetypes
> * at split_pfn_offset within the page. The split free page will be put into
> * separate migratetype lists afterwards. Otherwise, the function achieves
> * nothing.
> */
> -void split_free_page(struct page *free_page,
> - int order, unsigned long split_pfn_offset)
> +int split_free_page(struct page *free_page,
> + unsigned int order, unsigned long split_pfn_offset)
> {
> struct zone *zone = page_zone(free_page);
> unsigned long free_page_pfn = page_to_pfn(free_page);
> unsigned long pfn;
> unsigned long flags;
> int free_page_order;
> + int mt;
> + int ret = 0;
>
> if (split_pfn_offset == 0)
> - return;
> + return ret;
>
> spin_lock_irqsave(&zone->lock, flags);
> +
> + if (!PageBuddy(free_page) || buddy_order(free_page) != order) {
> + ret = -ENOENT;
> + goto out;
> + }
> +
> + mt = get_pageblock_migratetype(free_page);
> + if (likely(!is_migrate_isolate(mt)))
> + __mod_zone_freepage_state(zone, -(1UL << order), mt);
> +
> del_page_from_free_list(free_page, zone, order);
> for (pfn = free_page_pfn;
> pfn < free_page_pfn + (1UL << order);) {
> int mt = get_pfnblock_migratetype(pfn_to_page(pfn), pfn);
>
> - free_page_order = min_t(int,
> + free_page_order = min_t(unsigned int,
> pfn ? __ffs(pfn) : order,
> __fls(split_pfn_offset));
This part of the patch doesn't agree with any version of page_alloc.c I
have, but I was able to manually apply the change.
> __free_one_page(pfn_to_page(pfn), pfn, zone, free_page_order,
> @@ -1134,7 +1148,9 @@ void split_free_page(struct page *free_page,
> if (split_pfn_offset == 0)
> split_pfn_offset = (1UL << order) - (pfn - free_page_pfn);
> }
> +out:
> spin_unlock_irqrestore(&zone->lock, flags);
> + return ret;
> }
> /*
> * A bad page could be due to a number of fields. Instead of multiple branches,
> diff --git a/mm/page_isolation.c b/mm/page_isolation.c
> index c643c8420809..f539ccf7fb44 100644
> --- a/mm/page_isolation.c
> +++ b/mm/page_isolation.c
> @@ -300,7 +300,7 @@ __first_valid_page(unsigned long pfn, unsigned long nr_pages)
> * the in-use page then splitting the free page.
> */
> static int isolate_single_pageblock(unsigned long boundary_pfn, int flags,
> - gfp_t gfp_flags, bool isolate_before)
> + gfp_t gfp_flags, bool isolate_before, bool skip_isolation)
> {
> unsigned char saved_mt;
> unsigned long start_pfn;
> @@ -327,11 +327,16 @@ static int isolate_single_pageblock(unsigned long boundary_pfn, int flags,
> zone->zone_start_pfn);
>
> saved_mt = get_pageblock_migratetype(pfn_to_page(isolate_pageblock));
> - ret = set_migratetype_isolate(pfn_to_page(isolate_pageblock), saved_mt, flags,
> - isolate_pageblock, isolate_pageblock + pageblock_nr_pages);
>
> - if (ret)
> - return ret;
> + if (skip_isolation)
> + VM_BUG_ON(!is_migrate_isolate(saved_mt));
> + else {
> + ret = set_migratetype_isolate(pfn_to_page(isolate_pageblock), saved_mt, flags,
> + isolate_pageblock, isolate_pageblock + pageblock_nr_pages);
> +
> + if (ret)
> + return ret;
> + }
>
> /*
> * Bail out early when the to-be-isolated pageblock does not form
> @@ -367,8 +372,11 @@ static int isolate_single_pageblock(unsigned long boundary_pfn, int flags,
> int order = buddy_order(page);
>
> if (pfn + (1UL << order) > boundary_pfn)
> - split_free_page(page, order, boundary_pfn - pfn);
> - pfn += (1UL << order);
> + /* free page changed before split, check it again */
> + if (split_free_page(page, order, boundary_pfn - pfn))
> + continue;
> +
> + pfn += 1UL << order;
> continue;
> }
> /*
> @@ -463,7 +471,8 @@ static int isolate_single_pageblock(unsigned long boundary_pfn, int flags,
> return 0;
> failed:
> /* restore the original migratetype */
> - unset_migratetype_isolate(pfn_to_page(isolate_pageblock), saved_mt);
> + if (!skip_isolation)
> + unset_migratetype_isolate(pfn_to_page(isolate_pageblock), saved_mt);
> return -EBUSY;
> }
>
> @@ -522,14 +531,18 @@ int start_isolate_page_range(unsigned long start_pfn, unsigned long end_pfn,
> unsigned long isolate_start = ALIGN_DOWN(start_pfn, pageblock_nr_pages);
> unsigned long isolate_end = ALIGN(end_pfn, pageblock_nr_pages);
> int ret;
> + bool skip_isolation = false;
>
> /* isolate [isolate_start, isolate_start + pageblock_nr_pages) pageblock */
> - ret = isolate_single_pageblock(isolate_start, flags, gfp_flags, false);
> + ret = isolate_single_pageblock(isolate_start, flags, gfp_flags, false, skip_isolation);
> if (ret)
> return ret;
>
> + if (isolate_start == isolate_end - pageblock_nr_pages)
> + skip_isolation = true;
> +
> /* isolate [isolate_end - pageblock_nr_pages, isolate_end) pageblock */
> - ret = isolate_single_pageblock(isolate_end, flags, gfp_flags, true);
> + ret = isolate_single_pageblock(isolate_end, flags, gfp_flags, true, skip_isolation);
> if (ret) {
> unset_migratetype_isolate(pfn_to_page(isolate_start), migratetype);
> return ret;
>
>
> --
> Best Regards,
> Yan, Zi
This patch does appear to fix the problem I observed. I'll poke it a
little more, but so far it looks good.
Thanks!,
Doug
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