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Message-ID: <e657d5ac-6f92-4dbb-bf32-76084988d024@huaweicloud.com> Date: Mon, 8 Dec 2025 10:26:59 +0800 From: Chen Ridong <chenridong@...weicloud.com> To: Shakeel Butt <shakeel.butt@...ux.dev>, Johannes Weiner <hannes@...xchg.org> Cc: akpm@...ux-foundation.org, axelrasmussen@...gle.com, yuanchu@...gle.com, weixugc@...gle.com, david@...nel.org, lorenzo.stoakes@...cle.com, Liam.Howlett@...cle.com, vbabka@...e.cz, rppt@...nel.org, surenb@...gle.com, mhocko@...e.com, corbet@....net, hannes@...xchg.org, roman.gushchin@...ux.dev, muchun.song@...ux.dev, yuzhao@...gle.com, zhengqi.arch@...edance.com, linux-mm@...ck.org, linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org, cgroups@...r.kernel.org, lujialin4@...wei.com, chenridong@...wei.com Subject: Re: [RFC PATCH -next 1/2] mm/mglru: use mem_cgroup_iter for global reclaim On 2025/12/5 6:29, Shakeel Butt wrote: > Hi Chen, > > On Thu, Dec 04, 2025 at 12:31:23PM +0000, Chen Ridong wrote: >> From: Chen Ridong <chenridong@...wei.com> >> >> The memcg LRU was originally introduced for global reclaim to enhance >> scalability. However, its implementation complexity has led to performance >> regressions when dealing with a large number of memory cgroups [1]. >> >> As suggested by Johannes [1], this patch adopts mem_cgroup_iter with >> cookie-based iteration for global reclaim, aligning with the approach >> already used in shrink_node_memcgs. This simplification removes the >> dedicated memcg LRU tracking while maintaining the core functionality. >> >> It performed a stress test based on Zhao Yu's methodology [2] on a >> 1 TB, 4-node NUMA system. The results are summarized below: >> >> memcg LRU memcg iter >> stddev(pgsteal) / mean(pgsteal) 91.2% 75.7% >> sum(pgsteal) / sum(requested) 216.4% 230.5% >> >> The new implementation demonstrates a significant improvement in >> fairness, reducing the standard deviation relative to the mean by >> 15.5 percentage points. While the reclaim accuracy shows a slight >> increase in overscan (from 85086871 to 90633890, 6.5%). >> >> The primary benefits of this change are: >> 1. Simplified codebase by removing custom memcg LRU infrastructure >> 2. Improved fairness in memory reclaim across multiple cgroups >> 3. Better performance when creating many memory cgroups >> >> [1] https://lore.kernel.org/r/20251126171513.GC135004@cmpxchg.org >> [2] https://lore.kernel.org/r/20221222041905.2431096-7-yuzhao@google.com >> Signed-off-by: Chen Ridong <chenridong@...wei.com> > > Thanks a lot of this awesome work. > Hello Shakeel and Johannes, I apologize for the incorrect results I provided earlier. I initially used an AI tool to process the data (I admit that was lazy of me—please forget that). When I re-ran the test to re-extracted the refault data and processed it again, I found that the AI tool had given me the wrong output. I have now processed the data manually in Excel, and the correct results are: pgsteal： memcg LRU memcg iter stddev(pgsteal) / mean(pgsteal) 106.03% 93.20% sum(pgsteal) / sum(requested) 98.10% 99.28% workingset_refault_anon： memcg LRU memcg iter stddev(refault) / mean(refault) 193.97% 134.67% sum(refault) 1963229 2027567 I believe these final results are much better than the previous incorrect ones, especially since the pgsteal ratio is now close to 100%, indicating we are not over-scanning. Additionally, refaults increased by 64,238 (a 3.2% rise). Let me know if you have any questions. ---------------------------------------------------------------------- The original data memcg LRU: pgsteal: SUM: 38572704 AVERAGE: 301349.25 STDEV: 319518.5965 refault: SUM: 1963229 AVERAGE: 15337.72656 STDEV: 29750.03391 pgsteal 655392 workingset_refault_anon 17131 pgsteal 657308 workingset_refault_anon 24841 pgsteal 103777 workingset_refault_anon 430 pgsteal 103134 workingset_refault_anon 884 pgsteal 964772 workingset_refault_anon 117159 pgsteal 103462 workingset_refault_anon 539 pgsteal 102878 workingset_refault_anon 25 pgsteal 707851 workingset_refault_anon 30634 pgsteal 103925 workingset_refault_anon 497 pgsteal 103913 workingset_refault_anon 953 pgsteal 103020 workingset_refault_anon 110 pgsteal 102871 workingset_refault_anon 607 pgsteal 697775 workingset_refault_anon 21529 pgsteal 102944 workingset_refault_anon 57 pgsteal 103090 workingset_refault_anon 819 pgsteal 102988 workingset_refault_anon 583 pgsteal 102987 workingset_refault_anon 108 pgsteal 103093 workingset_refault_anon 17 pgsteal 778016 workingset_refault_anon 79000 pgsteal 102920 workingset_refault_anon 14 pgsteal 655447 workingset_refault_anon 9069 pgsteal 102869 workingset_refault_anon 6 pgsteal 699920 workingset_refault_anon 34409 pgsteal 103127 workingset_refault_anon 223 pgsteal 102876 workingset_refault_anon 646 pgsteal 103642 workingset_refault_anon 439 pgsteal 102881 workingset_refault_anon 110 pgsteal 863202 workingset_refault_anon 77605 pgsteal 651786 workingset_refault_anon 8322 pgsteal 102981 workingset_refault_anon 51 pgsteal 103380 workingset_refault_anon 877 pgsteal 706377 workingset_refault_anon 27729 pgsteal 103436 workingset_refault_anon 682 pgsteal 103839 workingset_refault_anon 336 pgsteal 103012 workingset_refault_anon 23 pgsteal 103476 workingset_refault_anon 729 pgsteal 102867 workingset_refault_anon 12 pgsteal 102914 workingset_refault_anon 122 pgsteal 102886 workingset_refault_anon 627 pgsteal 103736 workingset_refault_anon 514 pgsteal 102879 workingset_refault_anon 618 pgsteal 102860 workingset_refault_anon 3 pgsteal 102877 workingset_refault_anon 27 pgsteal 103255 workingset_refault_anon 384 pgsteal 982183 workingset_refault_anon 85362 pgsteal 102947 workingset_refault_anon 158 pgsteal 102880 workingset_refault_anon 651 pgsteal 973764 workingset_refault_anon 81542 pgsteal 923711 workingset_refault_anon 94596 pgsteal 102938 workingset_refault_anon 660 pgsteal 888882 workingset_refault_anon 69549 pgsteal 102868 workingset_refault_anon 14 pgsteal 103130 workingset_refault_anon 166 pgsteal 103388 workingset_refault_anon 467 pgsteal 102965 workingset_refault_anon 197 pgsteal 964699 workingset_refault_anon 74903 pgsteal 103263 workingset_refault_anon 373 pgsteal 103614 workingset_refault_anon 781 pgsteal 962228 workingset_refault_anon 72108 pgsteal 672174 workingset_refault_anon 19739 pgsteal 102920 workingset_refault_anon 19 pgsteal 670248 workingset_refault_anon 18411 pgsteal 102877 workingset_refault_anon 581 pgsteal 103758 workingset_refault_anon 871 pgsteal 102874 workingset_refault_anon 609 pgsteal 103075 workingset_refault_anon 274 pgsteal 103550 workingset_refault_anon 102 pgsteal 755180 workingset_refault_anon 44303 pgsteal 951252 workingset_refault_anon 84566 pgsteal 929144 workingset_refault_anon 99081 pgsteal 103207 workingset_refault_anon 30 pgsteal 103292 workingset_refault_anon 427 pgsteal 103271 workingset_refault_anon 332 pgsteal 102865 workingset_refault_anon 4 pgsteal 923280 workingset_refault_anon 72715 pgsteal 104682 workingset_refault_anon 372 pgsteal 102870 workingset_refault_anon 7 pgsteal 102902 workingset_refault_anon 661 pgsteal 103053 workingset_refault_anon 40 pgsteal 103685 workingset_refault_anon 540 pgsteal 103857 workingset_refault_anon 970 pgsteal 109210 workingset_refault_anon 2806 pgsteal 103627 workingset_refault_anon 319 pgsteal 104029 workingset_refault_anon 42 pgsteal 918361 workingset_refault_anon 90387 pgsteal 103489 workingset_refault_anon 626 pgsteal 103188 workingset_refault_anon 801 pgsteal 102875 workingset_refault_anon 11 pgsteal 102994 workingset_refault_anon 79 pgsteal 102910 workingset_refault_anon 43 pgsteal 102922 workingset_refault_anon 687 pgsteal 103941 workingset_refault_anon 1219 pgsteal 903622 workingset_refault_anon 113751 pgsteal 664357 workingset_refault_anon 27959 pgsteal 104947 workingset_refault_anon 11 pgsteal 701084 workingset_refault_anon 30665 pgsteal 650719 workingset_refault_anon 20810 pgsteal 641924 workingset_refault_anon 17137 pgsteal 933870 workingset_refault_anon 98393 pgsteal 633231 workingset_refault_anon 15924 pgsteal 102936 workingset_refault_anon 34 pgsteal 104020 workingset_refault_anon 781 pgsteal 104274 workingset_refault_anon 1841 pgsteal 621672 workingset_refault_anon 5891 pgsteal 103307 workingset_refault_anon 474 pgsteal 103386 workingset_refault_anon 27 pgsteal 103266 workingset_refault_anon 243 pgsteal 102896 workingset_refault_anon 15 pgsteal 103905 workingset_refault_anon 988 pgsteal 103104 workingset_refault_anon 304 pgsteal 104277 workingset_refault_anon 285 pgsteal 696374 workingset_refault_anon 24971 pgsteal 103009 workingset_refault_anon 775 pgsteal 103849 workingset_refault_anon 747 pgsteal 102867 workingset_refault_anon 9 pgsteal 700211 workingset_refault_anon 35289 pgsteal 102923 workingset_refault_anon 88 pgsteal 104139 workingset_refault_anon 789 pgsteal 105152 workingset_refault_anon 1257 pgsteal 102945 workingset_refault_anon 76 pgsteal 103227 workingset_refault_anon 343 pgsteal 102880 workingset_refault_anon 95 pgsteal 102967 workingset_refault_anon 101 pgsteal 989176 workingset_refault_anon 89597 pgsteal 694181 workingset_refault_anon 22499 pgsteal 784354 workingset_refault_anon 68311 pgsteal 102882 workingset_refault_anon 24 pgsteal 103108 workingset_refault_anon 24 ------------------------------------------------------------------- The original data memcg iter: pgsteal: SUM: 39036863 AVERAGE: 304975.4922 STDEV: 284226.526 refault: SUM: 2027567 AVERAGE: 15840.36719 STDEV: 21332.00262 pgsteal 103167 workingset_refault_anon 203 pgsteal 714044 workingset_refault_anon 42633 pgsteal 103209 workingset_refault_anon 581 pgsteal 103605 workingset_refault_anon 240 pgsteal 740909 workingset_refault_anon 53177 pgsteal 103089 workingset_refault_anon 141 pgsteal 726760 workingset_refault_anon 32624 pgsteal 104039 workingset_refault_anon 397 pgsteal 754667 workingset_refault_anon 56144 pgsteal 713916 workingset_refault_anon 41813 pgsteal 104104 workingset_refault_anon 307 pgsteal 109567 workingset_refault_anon 244 pgsteal 714194 workingset_refault_anon 47076 pgsteal 711693 workingset_refault_anon 35616 pgsteal 105026 workingset_refault_anon 2221 pgsteal 103442 workingset_refault_anon 269 pgsteal 112773 workingset_refault_anon 5086 pgsteal 715969 workingset_refault_anon 32457 pgsteal 127828 workingset_refault_anon 9579 pgsteal 102885 workingset_refault_anon 109 pgsteal 112156 workingset_refault_anon 2974 pgsteal 104242 workingset_refault_anon 948 pgsteal 701184 workingset_refault_anon 47940 pgsteal 104080 workingset_refault_anon 836 pgsteal 106606 workingset_refault_anon 2420 pgsteal 103666 workingset_refault_anon 129 pgsteal 103330 workingset_refault_anon 532 pgsteal 103639 workingset_refault_anon 275 pgsteal 108494 workingset_refault_anon 3814 pgsteal 103626 workingset_refault_anon 412 pgsteal 103697 workingset_refault_anon 577 pgsteal 103736 workingset_refault_anon 582 pgsteal 103360 workingset_refault_anon 281 pgsteal 116733 workingset_refault_anon 6674 pgsteal 102978 workingset_refault_anon 5 pgsteal 108945 workingset_refault_anon 3141 pgsteal 706630 workingset_refault_anon 33241 pgsteal 103426 workingset_refault_anon 134 pgsteal 715070 workingset_refault_anon 33575 pgsteal 102871 workingset_refault_anon 12 pgsteal 103617 workingset_refault_anon 776 pgsteal 767084 workingset_refault_anon 64710 pgsteal 104197 workingset_refault_anon 176 pgsteal 104488 workingset_refault_anon 1469 pgsteal 103253 workingset_refault_anon 228 pgsteal 702800 workingset_refault_anon 26424 pgsteal 107469 workingset_refault_anon 2838 pgsteal 104441 workingset_refault_anon 1562 pgsteal 123013 workingset_refault_anon 13117 pgsteal 737817 workingset_refault_anon 53330 pgsteal 103939 workingset_refault_anon 759 pgsteal 103568 workingset_refault_anon 783 pgsteal 122707 workingset_refault_anon 11944 pgsteal 103690 workingset_refault_anon 885 pgsteal 103456 workingset_refault_anon 145 pgsteal 104068 workingset_refault_anon 632 pgsteal 319368 workingset_refault_anon 12579 pgsteal 103912 workingset_refault_anon 304 pgsteal 119416 workingset_refault_anon 3350 pgsteal 717107 workingset_refault_anon 34764 pgsteal 107163 workingset_refault_anon 535 pgsteal 103299 workingset_refault_anon 142 pgsteal 103825 workingset_refault_anon 176 pgsteal 408564 workingset_refault_anon 14606 pgsteal 115785 workingset_refault_anon 4622 pgsteal 119234 workingset_refault_anon 9225 pgsteal 729060 workingset_refault_anon 54309 pgsteal 107149 workingset_refault_anon 536 pgsteal 708839 workingset_refault_anon 43133 pgsteal 695961 workingset_refault_anon 40182 pgsteal 723303 workingset_refault_anon 32298 pgsteal 103581 workingset_refault_anon 1305 pgsteal 699646 workingset_refault_anon 49924 pgsteal 717867 workingset_refault_anon 39229 pgsteal 104148 workingset_refault_anon 1318 pgsteal 104127 workingset_refault_anon 568 pgsteal 103168 workingset_refault_anon 322 pgsteal 103477 workingset_refault_anon 538 pgsteal 103022 workingset_refault_anon 60 pgsteal 103305 workingset_refault_anon 323 pgsteal 103812 workingset_refault_anon 1324 pgsteal 103139 workingset_refault_anon 126 pgsteal 723251 workingset_refault_anon 34206 pgsteal 103068 workingset_refault_anon 861 pgsteal 742515 workingset_refault_anon 54439 pgsteal 762161 workingset_refault_anon 52654 pgsteal 103934 workingset_refault_anon 889 pgsteal 104065 workingset_refault_anon 315 pgsteal 383893 workingset_refault_anon 25036 pgsteal 107929 workingset_refault_anon 2367 pgsteal 726127 workingset_refault_anon 45809 pgsteal 675291 workingset_refault_anon 66534 pgsteal 105585 workingset_refault_anon 2323 pgsteal 105098 workingset_refault_anon 1625 pgsteal 104264 workingset_refault_anon 718 pgsteal 741873 workingset_refault_anon 47045 pgsteal 103466 workingset_refault_anon 70 pgsteal 723870 workingset_refault_anon 58780 pgsteal 104740 workingset_refault_anon 521 pgsteal 740739 workingset_refault_anon 45099 pgsteal 752994 workingset_refault_anon 53713 pgsteal 110164 workingset_refault_anon 2572 pgsteal 711304 workingset_refault_anon 41135 pgsteal 746870 workingset_refault_anon 60298 pgsteal 729166 workingset_refault_anon 42594 pgsteal 110138 workingset_refault_anon 1511 pgsteal 103836 workingset_refault_anon 675 pgsteal 116821 workingset_refault_anon 3952 pgsteal 104967 workingset_refault_anon 2035 pgsteal 711362 workingset_refault_anon 31458 pgsteal 103835 workingset_refault_anon 507 pgsteal 113846 workingset_refault_anon 2997 pgsteal 104406 workingset_refault_anon 1724 pgsteal 103551 workingset_refault_anon 1293 pgsteal 705340 workingset_refault_anon 44234 pgsteal 728076 workingset_refault_anon 29849 pgsteal 103829 workingset_refault_anon 254 pgsteal 103700 workingset_refault_anon 712 pgsteal 103382 workingset_refault_anon 506 pgsteal 728881 workingset_refault_anon 60152 pgsteal 614645 workingset_refault_anon 43956 pgsteal 107672 workingset_refault_anon 2768 pgsteal 123550 workingset_refault_anon 11937 pgsteal 103747 workingset_refault_anon 899 pgsteal 747657 workingset_refault_anon 50264 pgsteal 110949 workingset_refault_anon 1422 pgsteal 103596 workingset_refault_anon 278 pgsteal 742471 workingset_refault_anon 69586 -- Best regards, Ridong
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