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

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Message-ID: <CAOUHufaO-hxdEJZtdN-5EHEs-wOJoGQ1pVGeHaa89L7hSz8grQ@mail.gmail.com>
Date: Wed, 17 Jul 2024 09:44:33 -0600
From: Yu Zhao <yuzhao@...gle.com>
To: Janosch Frank <frankja@...ux.ibm.com>, kernel test robot <oliver.sang@...el.com>
Cc: oe-lkp@...ts.linux.dev, lkp@...el.com, 
	Linux Memory Management List <linux-mm@...ck.org>, Andrew Morton <akpm@...ux-foundation.org>, 
	Muchun Song <muchun.song@...ux.dev>, 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>, linux-kernel@...r.kernel.org, 
	ying.huang@...el.com, feng.tang@...el.com, fengwei.yin@...el.com, 
	Christian Borntraeger <borntraeger@...ux.ibm.com>, Claudio Imbrenda <imbrenda@...ux.ibm.com>, 
	Marc Hartmayer <mhartmay@...ux.ibm.com>, Heiko Carstens <hca@...ux.ibm.com>, 
	Yosry Ahmed <yosryahmed@...gle.com>
Subject: Re: [linux-next:master] [mm/hugetlb_vmemmap] 875fa64577:
 vm-scalability.throughput -34.3% regression

On Wed, Jul 17, 2024 at 2:36 AM Yu Zhao <yuzhao@...gle.com> wrote:
>
> Hi Janosch and Oliver,
>
> On Wed, Jul 17, 2024 at 1:57 AM Janosch Frank <frankja@...ux.ibm.com> wrote:
> >
> > On 7/9/24 07:11, kernel test robot 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")
> > > https://git.kernel.org/cgit/linux/kernel/git/next/linux-next.git master
> > >
> > > [still regression on linux-next/master 0b58e108042b0ed28a71cd7edf5175999955b233]
> > >
> > This has hit s390 huge page backed KVM guests as well.
> > Our simple start/stop test case went from ~5 to over 50 seconds of runtime.
>
> Could you try the attached patch please? Thank you.

Thanks, Yosry, for spotting the following typo:
  flags &= VMEMMAP_SYNCHRONIZE_RCU;
It's supposed to be:
  flags &= ~VMEMMAP_SYNCHRONIZE_RCU;

Reattaching v2 with the above typo fixed. Please let me know, Janosch & Oliver.

Download attachment "hugetlb-fix-v2.patch" of type "application/octet-stream" (3953 bytes)