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From: Mike Kravetz <mike.kravetz@oracle.com>
To: Vlastimil Babka <vbabka@suse.cz>,
	Andrew Morton <akpm@linux-foundation.org>
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org,
	David Hildenbrand <david@redhat.com>,
	Michal Hocko <mhocko@suse.com>,
	Oscar Salvador <osalvador@suse.de>, Zi Yan <ziy@nvidia.com>,
	Muchun Song <songmuchun@bytedance.com>,
	Naoya Horiguchi <naoya.horiguchi@linux.dev>,
	David Rientjes <rientjes@google.com>,
	Hillf Danton <hdanton@sina.com>
Subject: Re: [PATCH RESEND 0/8] hugetlb: add demote/split page functionality
Date: Thu, 2 Sep 2021 11:17:06 -0700	[thread overview]
Message-ID: <02a1a50f-4e7c-4eb7-519c-35b26ec2c6af@oracle.com> (raw)
In-Reply-To: <b3b334ea-0e6f-ced9-e444-df4ec49455a0@suse.cz>

On 8/30/21 3:11 AM, Vlastimil Babka wrote:
> On 8/28/21 01:04, Mike Kravetz wrote:
>> On 8/27/21 10:22 AM, Vlastimil Babka wrote:
>> I 'may' have been over stressing the system with all CPUs doing file
>> reads to fill the page cache with clean pages.  I certainly need to
>> spend some more debug/analysis time on this.
> 
> Hm that *could* play a role, as these will allow reclaim to make progress, but
> also the reclaimed pages might be stolen immediately and compaction will return
> COMPACT_SKIPPED and in should_compact_retry() we might go through this code path:
> 
>         /*      
>          * compaction was skipped because there are not enough order-0 pages
>          * to work with, so we retry only if it looks like reclaim can help.
>          */
>         if (compaction_needs_reclaim(compact_result)) {
>                 ret = compaction_zonelist_suitable(ac, order, alloc_flags);
>                 goto out;
>         }       
> 
> where compaction_zonelist_suitable() will return true because it appears
> reclaim can free pages to allow progress. And there are no max retries
> applied for this case.
> With the reclaim and compaction tracepoints it should be possible to
> confirm this scenario.

Here is some very high level information from a long stall that was
interrupted.  This was an order 9 allocation from alloc_buddy_huge_page().

55269.530564] __alloc_pages_slowpath: jiffies 47329325 tries 609673 cpu_tries 1   node 0 FAIL
[55269.539893]     r_tries 25       c_tries 609647   reclaim 47325161 compact 607     

Yes, in __alloc_pages_slowpath for 47329325 jiffies before being interrupted.
should_reclaim_retry returned true 25 times and should_compact_retry returned
true 609647 times.
Almost all time (47325161 jiffies) spent in __alloc_pages_direct_reclaim, and
607 jiffies spent in __alloc_pages_direct_compact.

Looks like both
reclaim retries > MAX_RECLAIM_RETRIES
and
compaction retries > MAX_COMPACT_RETRIES
-- 
Mike Kravetz

  reply	other threads:[~2021-09-02 18:17 UTC|newest]

Thread overview: 38+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-16 22:49 Mike Kravetz
2021-08-16 22:49 ` [PATCH 1/8] hugetlb: add demote hugetlb page sysfs interfaces Mike Kravetz
2021-08-16 22:49 ` [PATCH 2/8] hugetlb: add HPageCma flag and code to free non-gigantic pages in CMA Mike Kravetz
2021-08-16 22:49 ` [PATCH 3/8] hugetlb: add demote bool to gigantic page routines Mike Kravetz
2021-08-16 22:49 ` [PATCH 4/8] hugetlb: add hugetlb demote page support Mike Kravetz
2021-08-16 22:49 ` [PATCH 5/8] hugetlb: document the demote sysfs interfaces Mike Kravetz
2021-08-16 23:28   ` Andrew Morton
2021-08-17  1:04     ` Mike Kravetz
2021-09-21 13:52   ` Aneesh Kumar K.V
2021-09-21 17:17     ` Mike Kravetz
2021-08-16 22:49 ` [PATCH 6/8] hugetlb: vmemmap optimizations when demoting hugetlb pages Mike Kravetz
2021-08-16 22:49 ` [PATCH 7/8] hugetlb: prepare destroy and prep routines for vmemmap optimized pages Mike Kravetz
2021-08-16 22:49 ` [PATCH 8/8] hugetlb: Optimized demote vmemmap optimizatized pages Mike Kravetz
2021-08-16 23:23 ` [PATCH RESEND 0/8] hugetlb: add demote/split page functionality Andrew Morton
2021-08-17  0:17   ` Mike Kravetz
2021-08-17  0:39     ` Andrew Morton
2021-08-17  0:58       ` Mike Kravetz
2021-08-16 23:27 ` Andrew Morton
2021-08-17  0:46   ` Mike Kravetz
2021-08-17  1:46     ` Andrew Morton
2021-08-17  7:30       ` David Hildenbrand
2021-08-17 16:19         ` Mike Kravetz
2021-08-17 18:49           ` David Hildenbrand
2021-08-24 22:08       ` Mike Kravetz
2021-08-27 17:22         ` Vlastimil Babka
2021-08-27 23:04           ` Mike Kravetz
2021-08-30 10:11             ` Vlastimil Babka
2021-09-02 18:17               ` Mike Kravetz [this message]
2021-09-06 14:40                 ` Vlastimil Babka
     [not found]                 ` <20210907085001.3773-1-hdanton@sina.com>
2021-09-08 21:00                   ` Mike Kravetz
2021-09-09 11:54                     ` Michal Hocko
2021-09-09 13:45                       ` Vlastimil Babka
2021-09-09 21:31                         ` Mike Kravetz
2021-09-10  8:20                         ` Michal Hocko
2021-09-11  0:11                           ` Mike Kravetz
2021-09-13 15:50                             ` Michal Hocko
2021-09-15 16:57                               ` Mike Kravetz
2021-09-17 20:44                                 ` Mike Kravetz

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