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 vKsfmti0 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 4/9/26 12:37 PM, Haakon Bugge wrote: >> On 8 Apr 2026, at 16:27, Joseph Salisbury wrote: >> >> >> >> On 4/8/26 4:09 AM, David Hildenbrand (Arm) wrote: >>>>> It was also found that adding '--mremap-numa' changes the behavior >>>>> substantially: >>>> "assign memory mapped pages to randomly selected NUMA nodes. This is >>>> disabled for systems that do not support NUMA." >>>> >>>> so this is just sharding your lock contention across your NUMA nodes (you >>>> have an lruvec per node). >>>> >>>>> stress-ng --mremap 8192 --mremap-bytes 4K --timeout 30 --mremap-numa >>>>> --metrics-brief >>>>> >>>>> mremap 2570798 29.39 8.06 106.23 87466.50 22494.74 >>>>> >>>>> So it's possible that either actual swapping, or the mbind(..., >>>>> MPOL_MF_MOVE) path used by '--mremap-numa', removes most of the excessive >>>>> system time. >>>>> >>>>> Does this look like a known MM scalability issue around short-lived >>>>> MAP_POPULATE / munmap churn? >>>> Yes. Is this an actual issue on some workload? >>> Same thought, it's unclear to me why we should care here. In particular, >>> when talking about excessive use of zero-filled pages. >>> >> Currently this is only showing up with that particular stress test. We will try John's patch and provide feedback. >> >> Thanks for all the feedback, everyone! > I reported this internally and have worked with Joseph on it. I tested v7.0-rc7-68-g7f87a5ea75f01 ("-"), "Base", vs. ditto plus John Hubbard's patch ("+"), "Test". > > Stress-ng command: stress-ng --mremap 8192 --mremap-bytes 4K --timeout 30 --metrics-brief > > System is an AMD EPYC 9J45: > NUMA node(s): 2 > NUMA node0 CPU(s): 0-127,256-383 > NUMA node1 CPU(s): 128-255,384-511 > > The stress-ng command was run ten times and here are the averages and pstdev: > > bogo ops/s pstdev system time pstdev > (realtime) > -------------------------------------------- > - 3192638 35% 24041 32% > + 3657904 5% 15278 0% > > This is 15% improvement in bogo ops/s (realtime) and a decent 36% reduction in system time. > > I shamelessly copied and modified the fio command from [1]. I ran: > > # fio -filename=/dev/nvme0n1 -direct=0 -thread -size=1024G -rwmixwrite=30 \ > --norandommap --randrepeat=0 -ioengine=mmap -bs=4k -numjobs=1024 -runtime=3600 \ > --time_based -group_reporting -name=mytest > > (that is, one hour runtime) > > - read: IOPS=14.0M, BW=53.4GiB/s (57.3GB/s)(188TiB/3608413msec) > + read: IOPS=16.0M, BW=61.2GiB/s (65.7GB/s)(215TiB/3600051msec) > - READ: bw=53.4GiB/s (57.3GB/s), 53.4GiB/s-53.4GiB/s (57.3GB/s-57.3GB/s), io=188TiB (207TB), run=3608413-3608413msec > + READ: bw=61.2GiB/s (65.7GB/s), 61.2GiB/s-61.2GiB/s (65.7GB/s-65.7GB/s), io=215TiB (237TB), run=3600051-3600051msec > > Also, running Base, I see tons of: > > Jobs: 726 (f=726): [_(2),R(1),_(1),R(3),_(4),R(6),_(1),R(2),_(2),R(2),_(3),R(1),_(5),R(2),_(1),R(2),_(1),R(1),_(2),R(2),_(1),R(1),_(1),R(2),_(1),R(3),_(1),R(3),_(1),R(1),_(1),R(1),_(1),R(1),_(1),R(3),_(1),R(3),_(1),R(1),_(3),R(1),_(1),R(5),_(1),R(5),_(1),R(1),_(2),R(1),_(4),R(2),_(1),R(3),_(1),R(3),_(1),R(1),_(2),R(1),_(1),R(8),_(1),R(4),_(1),R(3),_(1),R(1),_(1),R(2),_(1),R(7),_(2),R(2) > > when the fio test terminates, which I do not see using Test. I take that as the threads do not terminate timely using the Base kernel. > > > Thxs, Håkon > > > [1] https://lkml.org/lkml/2024/7/3/1049 > > Adding Lorenzo Stoakes to Cc.