linux-kernel - Re: [LKP] [hugetlbfs] 9c83282117: vm-scalability.throughput -4.3% regression

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Message-ID: <21117eab-862e-562b-0c86-ec2ccc1f68e4@oracle.com>
Date:   Wed, 2 Jan 2019 08:54:07 -0800
From:   Mike Kravetz <mike.kravetz@...cle.com>
To:     kernel test robot <rong.a.chen@...el.com>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Michal Hocko <mhocko@...nel.org>,
        Hugh Dickins <hughd@...gle.com>,
        Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
        "Aneesh Kumar K . V" <aneesh.kumar@...ux.vnet.ibm.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
        Davidlohr Bueso <dave@...olabs.net>,
        Prakash Sangappa <prakash.sangappa@...cle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        stable@...r.kernel.org, lkp@...org
Subject: Re: [LKP] [hugetlbfs] 9c83282117: vm-scalability.throughput -4.3%
 regression

On 12/28/18 6:26 AM, kernel test robot wrote:
> Greeting,
> 
> FYI, we noticed a -4.3% regression of vm-scalability.throughput due to commit:
> 
> 
> commit: 9c83282117778856d647ffc461c4aede2abb6742 ("[PATCH v3 1/2] hugetlbfs: use i_mmap_rwsem for more pmd sharing synchronization")
> url: https://github.com/0day-ci/linux/commits/Mike-Kravetz/hugetlbfs-use-i_mmap_rwsem-for-better-synchronization/20181223-095226
> 
> 
> in testcase: vm-scalability
> on test machine: 104 threads Intel(R) Xeon(R) Platinum 8170 CPU @ 2.10GHz with 64G memory
> with following parameters:
> 
> 	runtime: 300s
> 	size: 8T
> 	test: anon-cow-seq-hugetlb
> 	cpufreq_governor: performance
> 	ucode: 0x200004d

I'll take a closer look.

The patch does introduce longer i_mmap_rwsem hold times for the sake of
correctness.  Need to more fully understand the test and results to determine
if this is expected.

-- 
Mike Kravetz