linux-kernel - Re: [linus:master] [mm] f822a9a81a: stress-ng.bigheap.realloc_calls_per

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Message-ID: <9e3a59b2-11c0-43ca-aff3-414091f04aa4@lucifer.local>
Date: Thu, 7 Aug 2025 09:27:41 +0100
From: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
To: kernel test robot <oliver.sang@...el.com>
Cc: Dev Jain <dev.jain@....com>, oe-lkp@...ts.linux.dev, lkp@...el.com,
        linux-kernel@...r.kernel.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        Barry Song <baohua@...nel.org>, Pedro Falcato <pfalcato@...e.de>,
        Anshuman Khandual <anshuman.khandual@....com>,
        Bang Li <libang.li@...group.com>,
        Baolin Wang <baolin.wang@...ux.alibaba.com>,
        bibo mao <maobibo@...ngson.cn>, David Hildenbrand <david@...hat.com>,
        Hugh Dickins <hughd@...gle.com>, Ingo Molnar <mingo@...nel.org>,
        Jann Horn <jannh@...gle.com>, Lance Yang <ioworker0@...il.com>,
        Liam Howlett <liam.howlett@...cle.com>,
        Matthew Wilcox <willy@...radead.org>, Peter Xu <peterx@...hat.com>,
        Qi Zheng <zhengqi.arch@...edance.com>,
        Ryan Roberts <ryan.roberts@....com>, Vlastimil Babka <vbabka@...e.cz>,
        Yang Shi <yang@...amperecomputing.com>, Zi Yan <ziy@...dia.com>,
        linux-mm@...ck.org
Subject: Re: [linus:master] [mm]  f822a9a81a:
 stress-ng.bigheap.realloc_calls_per_sec 37.3% regression

On Thu, Aug 07, 2025 at 04:17:09PM +0800, kernel test robot wrote:
>
>
> Hello,
>
> kernel test robot noticed a 37.3% regression of stress-ng.bigheap.realloc_calls_per_sec on:
>

Dev - could you please investigate and provide a fix for this as a
priority? As these numbers are quite scary (unless they're somehow super
synthetic or not meaningful or something).

>
> commit: f822a9a81a31311d67f260aea96005540b18ab07 ("mm: optimize mremap() by PTE batching")
> https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git master
>
> [still regression on      linus/master 186f3edfdd41f2ae87fc40a9ccba52a3bf930994]
> [still regression on linux-next/master b9ddaa95fd283bce7041550ddbbe7e764c477110]
>
> testcase: stress-ng
> config: x86_64-rhel-9.4
> compiler: gcc-12
> test machine: 192 threads 2 sockets Intel(R) Xeon(R) Platinum 8468V  CPU @ 2.4GHz (Sapphire Rapids) with 384G memory
> parameters:
>
> 	nr_threads: 100%
> 	testtime: 60s
> 	test: bigheap
> 	cpufreq_governor: performance
>
>
>
>
> If you fix the issue in a separate patch/commit (i.e. not just a new version of
> the same patch/commit), kindly add following tags
> | Reported-by: kernel test robot <oliver.sang@...el.com>
> | Closes: https://lore.kernel.org/oe-lkp/202508071609.4e743d7c-lkp@intel.com
>
>
> Details are as below:
> -------------------------------------------------------------------------------------------------->
>
>
> The kernel config and materials to reproduce are available at:
> https://download.01.org/0day-ci/archive/20250807/202508071609.4e743d7c-lkp@intel.com
>
> =========================================================================================
> compiler/cpufreq_governor/kconfig/nr_threads/rootfs/tbox_group/test/testcase/testtime:
>   gcc-12/performance/x86_64-rhel-9.4/100%/debian-12-x86_64-20240206.cgz/igk-spr-2sp1/bigheap/stress-ng/60s
>
> commit:
>   94dab12d86 ("mm: call pointers to ptes as ptep")
>   f822a9a81a ("mm: optimize mremap() by PTE batching")
>
> 94dab12d86cf77ff f822a9a81a31311d67f260aea96
> ---------------- ---------------------------
>          %stddev     %change         %stddev
>              \          |                \
>      13777 ± 37%     +45.0%      19979 ± 27%  numa-vmstat.node1.nr_slab_reclaimable
>     367205            +2.3%     375703        vmstat.system.in
>      55106 ± 37%     +45.1%      79971 ± 27%  numa-meminfo.node1.KReclaimable
>      55106 ± 37%     +45.1%      79971 ± 27%  numa-meminfo.node1.SReclaimable
>     559381           -37.3%     350757        stress-ng.bigheap.realloc_calls_per_sec
>      11468            +1.2%      11603        stress-ng.time.system_time
>     296.25            +4.5%     309.70        stress-ng.time.user_time
>       0.81 ±187%    -100.0%       0.00        perf-sched.sch_delay.avg.ms.__cond_resched.zap_pte_range.zap_pmd_range.isra.0
>       9.36 ±165%    -100.0%       0.00        perf-sched.sch_delay.max.ms.__cond_resched.zap_pte_range.zap_pmd_range.isra.0
>       0.81 ±187%    -100.0%       0.00        perf-sched.wait_time.avg.ms.__cond_resched.zap_pte_range.zap_pmd_range.isra.0
>       9.36 ±165%    -100.0%       0.00        perf-sched.wait_time.max.ms.__cond_resched.zap_pte_range.zap_pmd_range.isra.0
>       5.50 ± 17%    +390.9%      27.00 ± 56%  perf-c2c.DRAM.local
>     388.50 ± 10%    +114.7%     834.17 ± 33%  perf-c2c.DRAM.remote
>       1214 ± 13%    +107.3%       2517 ± 31%  perf-c2c.HITM.local
>     135.00 ± 19%    +130.9%     311.67 ± 32%  perf-c2c.HITM.remote
>       1349 ± 13%    +109.6%       2829 ± 31%  perf-c2c.HITM.total

Yeah this also looks pretty consistent too...

Yikes.