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From: Vlastimil Babka <vbabka@suse.cz>
To: Eric Dumazet <edumazet@google.com>
Cc: kernel test robot <oliver.sang@intel.com>,
	Mel Gorman <mgorman@techsingularity.net>,
	0day robot <lkp@intel.com>, Michal Hocko <mhocko@kernel.org>,
	Shakeel Butt <shakeelb@google.com>, Wei Xu <weixugc@google.com>,
	Greg Thelen <gthelen@google.com>, Hugh Dickins <hughd@google.com>,
	David Rientjes <rientjes@google.com>,
	LKML <linux-kernel@vger.kernel.org>,
	lkp@lists.01.org, "Huang, Ying" <ying.huang@intel.com>,
	"Tang, Feng" <feng.tang@intel.com>,
	zhengjun.xing@linux.intel.com, fengwei.yin@intel.com,
	Eric Dumazet <eric.dumazet@gmail.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	linux-mm <linux-mm@kvack.org>
Subject: Re: [mm/page_alloc] 8212a964ee: vm-scalability.throughput 30.5% improvement
Date: Sun, 13 Mar 2022 10:28:01 +0100	[thread overview]
Message-ID: <8f499c76-68cb-a2c3-01fd-c8759e2fd317@suse.cz> (raw)
In-Reply-To: <CANn89i+fM0k+=Qw0M0fso1f-Ya8--5+==gtcWqCpo=Gu-ca1Ow@mail.gmail.com>

On 3/13/22 00:26, Eric Dumazet wrote:
> On Sat, Mar 12, 2022 at 10:59 AM Vlastimil Babka <vbabka@suse.cz> wrote:
>>
>> On 3/12/22 16:43, kernel test robot wrote:
>>>
>>>
>>> Greeting,
>>>
>>> FYI, we noticed a 30.5% improvement of vm-scalability.throughput due to commit:
>>>
>>>
>>> commit: 8212a964ee020471104e34dce7029dec33c218a9 ("Re: [PATCH v2] mm/page_alloc: call check_new_pages() while zone spinlock is not held")
>>> url: https://github.com/0day-ci/linux/commits/Mel-Gorman/Re-PATCH-v2-mm-page_alloc-call-check_new_pages-while-zone-spinlock-is-not-held/20220309-203504
>>> patch link: https://lore.kernel.org/lkml/20220309123245.GI15701@techsingularity.net
>>
>> Heh, that's weird. I would expect some improvement from Eric's patch,
>> but this seems to be actually about Mel's "mm/page_alloc: check
>> high-order pages for corruption during PCP operations" applied directly
>> on 5.17-rc7 per the github url above. This was rather expected to make
>> performance worse if anything, so maybe the improvement is due to some
>> unexpected side-effect of different inlining decisions or cache alignment...
>>
> 
> I doubt this has anything to do with inlining or cache alignment.
> 
> I am not familiar with the benchmark, but its name
> (anon-w-rand-hugetlb) hints at hugetlb ?
> 
> After Mel fix, we go over 512 'struct page' to perform sanity checks,
> thus loading into cpu caches the 512 cache lines.

Ah, that's true.

> This caching is done while no lock is held.

But I don't think this is. The test was AFAICS done without your patch,
so the lock is still held in rmqueue(). And it's also held in
rmqueue_bulk() -> check_pcp_refill().

> If after this huge page allocation some mm operation needs to access
> these 512 struct pages,
> while holding a lock, then sure, there is a huge gain.


  reply	other threads:[~2022-03-13  9:29 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-03-04 17:02 [PATCH v2] mm/page_alloc: call check_new_pages() while zone spinlock is not held Eric Dumazet
2022-03-04 19:19 ` Shakeel Butt
2022-03-06 22:15 ` David Rientjes
2022-03-07  9:15 ` Mel Gorman
2022-03-08 23:49   ` Eric Dumazet
2022-03-09 12:32     ` Mel Gorman
2022-03-09 17:32       ` Eric Dumazet
2022-03-12 15:43       ` [mm/page_alloc] 8212a964ee: vm-scalability.throughput 30.5% improvement kernel test robot
2022-03-12 18:58         ` Vlastimil Babka
2022-03-12 23:26           ` Eric Dumazet
2022-03-13  9:28             ` Vlastimil Babka [this message]
2022-03-13 21:10               ` Eric Dumazet
2022-03-13 21:18                 ` Matthew Wilcox
2022-03-13 21:27                   ` Eric Dumazet
2022-03-13 21:36                     ` Eric Dumazet
2022-03-14  9:09                 ` Vlastimil Babka
2022-03-07  9:24 ` [PATCH v2] mm/page_alloc: call check_new_pages() while zone spinlock is not held Vlastimil Babka

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