linux-kernel - Re: [linux-next:master] [mm/hugetlb_vmemmap] 875fa64577: vm-scalability.throughput -34.3% regression

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Message-Id: <CB8E06DE-0DB7-4605-AB19-19CF4F0F17B9@linux.dev>
Date: Mon, 15 Jul 2024 10:40:43 +0800
From: Muchun Song <muchun.song@...ux.dev>
To: Oliver Sang <oliver.sang@...el.com>
Cc: Yu Zhao <yuzhao@...gle.com>,
 oe-lkp@...ts.linux.dev,
 kernel test robot <lkp@...el.com>,
 Linux Memory Management List <linux-mm@...ck.org>,
 Andrew Morton <akpm@...ux-foundation.org>,
 David Hildenbrand <david@...hat.com>,
 Frank van der Linden <fvdl@...gle.com>,
 Matthew Wilcox <willy@...radead.org>,
 Peter Xu <peterx@...hat.com>,
 Yang Shi <yang@...amperecomputing.com>,
 LKML <linux-kernel@...r.kernel.org>,
 Huang Ying <ying.huang@...el.com>,
 Feng Tang <feng.tang@...el.com>,
 Yin Fengwei <fengwei.yin@...el.com>
Subject: Re: [linux-next:master] [mm/hugetlb_vmemmap] 875fa64577:
 vm-scalability.throughput -34.3% regression



> On Jul 14, 2024, at 20:26, Oliver Sang <oliver.sang@...el.com> wrote:
> 
> hi, Yu Zhao,
> 
> On Wed, Jul 10, 2024 at 12:22:40AM -0600, Yu Zhao wrote:
>> On Mon, Jul 8, 2024 at 11:11 PM kernel test robot <oliver.sang@...el.com> wrote:
>>> 
>>> Hello,
>>> 
>>> kernel test robot noticed a -34.3% regression of vm-scalability.throughput on:
>>> 
>>> 
>>> commit: 875fa64577da9bc8e9963ee14fef8433f20653e7 ("mm/hugetlb_vmemmap: fix race with speculative PFN walkers")
>> 
>> This is likely caused by synchronize_rcu() wandering into the
>> allocation path. I'll patch that up soon.
>> 
> 
> we noticed this commit has already been merged into mainline
> 
> [bd225530a4c717714722c3731442b78954c765b3] mm/hugetlb_vmemmap: fix race with speculative PFN walkers
> branch: linus/master

Did you test with HVO enabled (there are two ways to enable HVO: 1) adding cmdline with "hugetlb_free_vmemmap=on"
or 2) write 1 to /proc/sys/vm/hugetlb_optimize_vmemmap)? I want to confirm if the regression is related
to HVO routine.

Thanks.

> 
> and the regression still exists in our tests. do you want us to test your
> patch? Thanks!