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Message-ID: <f3dc34f1-0579-412e-89a6-20e36ec67a7f@lucifer.local>
Date: Fri, 28 Nov 2025 07:49:42 +0000
From: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
To: Hongru Zhang <zhanghongru06@...il.com>
Cc: akpm@...ux-foundation.org, vbabka@...e.cz, david@...nel.org,
linux-mm@...ck.org, linux-kernel@...r.kernel.org, surenb@...gle.com,
mhocko@...e.com, jackmanb@...gle.com, hannes@...xchg.org,
ziy@...dia.com, Liam.Howlett@...cle.com, rppt@...nel.org,
axelrasmussen@...gle.com, yuanchu@...gle.com, weixugc@...gle.com,
Hongru Zhang <zhanghongru@...omi.com>
Subject: Re: [PATCH 0/3] mm: add per-migratetype counts to buddy allocator
and optimize pagetypeinfo access
Just a general plea :) could we please try not to send larger series like
this so late.
We're at the last day before the merge window, this is better sent during
6.19-rc1 or if now as an RFC.
Thanks, Lorenzo
On Fri, Nov 28, 2025 at 11:10:11AM +0800, Hongru Zhang wrote:
> On mobile devices, some user-space memory management components check
> memory pressure and fragmentation status periodically or via PSI, and
> take actions such as killing processes or performing memory compaction
> based on this information.
>
> Under high load scenarios, reading /proc/pagetypeinfo causes memory
> management components or memory allocation/free paths to be blocked
> for extended periods waiting for the zone lock, leading to the following
> issues:
> 1. Long interrupt-disabled spinlocks - occasionally exceeding 10ms on Qcom
> 8750 platforms, reducing system real-time performance
> 2. Memory management components being blocked for extended periods,
> preventing rapid acquisition of memory fragmentation information for
> critical memory management decisions and actions
> 3. Increased latency in memory allocation and free paths due to prolonged
> zone lock contention
>
> Changes:
> 1. Add per-migratetype counts to the buddy allocator to track free page
> block counts for each migratetype and order
> 2. Optimize /proc/pagetypeinfo access by utilizing these per-migratetype
> counts instead of iterating through free lists under zone lock
>
> Performance testing shows following improvements:
> 1. /proc/pagetypeinfo access latency reduced
>
> +-----------------------+----------+------------+
> | | no-patch | with-patch |
> +-----------------------+----------+------------+
> | Just after boot | 700.9 us | 268.6 us |
> +-----------------------+----------+------------+
> | After building kernel | 28.7 ms | 269.8 us |
> +-----------------------+----------+------------+
>
> 2. When /proc/pagetypeinfo is accessed concurrently, memory allocation and
> free performance degradation is reduced compared to the previous
> implementation
>
> Test setup:
> - Using config-pagealloc-micro
> - Monitor set to proc-pagetypeinfo, update frequency set to 10ms
> - PAGEALLOC_ORDER_MIN=4, PAGEALLOC_ORDER_MAX=4
>
> Without patch test results:
> vanilla vanilla
> no-monitor monitor
> Min alloc-odr4-1 8539.00 ( 0.00%) 8762.00 ( -2.61%)
> Min alloc-odr4-2 6501.00 ( 0.00%) 6683.00 ( -2.80%)
> Min alloc-odr4-4 5537.00 ( 0.00%) 5873.00 ( -6.07%)
> Min alloc-odr4-8 5030.00 ( 0.00%) 5361.00 ( -6.58%)
> Min alloc-odr4-16 4782.00 ( 0.00%) 5162.00 ( -7.95%)
> Min alloc-odr4-32 5838.00 ( 0.00%) 6499.00 ( -11.32%)
> Min alloc-odr4-64 6565.00 ( 0.00%) 7413.00 ( -12.92%)
> Min alloc-odr4-128 6896.00 ( 0.00%) 7898.00 ( -14.53%)
> Min alloc-odr4-256 7303.00 ( 0.00%) 8163.00 ( -11.78%)
> Min alloc-odr4-512 10179.00 ( 0.00%) 11985.00 ( -17.74%)
> Min alloc-odr4-1024 11000.00 ( 0.00%) 12165.00 ( -10.59%)
> Min free-odr4-1 820.00 ( 0.00%) 1230.00 ( -50.00%)
> Min free-odr4-2 511.00 ( 0.00%) 952.00 ( -86.30%)
> Min free-odr4-4 347.00 ( 0.00%) 434.00 ( -25.07%)
> Min free-odr4-8 286.00 ( 0.00%) 399.00 ( -39.51%)
> Min free-odr4-16 250.00 ( 0.00%) 405.00 ( -62.00%)
> Min free-odr4-32 294.00 ( 0.00%) 405.00 ( -37.76%)
> Min free-odr4-64 333.00 ( 0.00%) 363.00 ( -9.01%)
> Min free-odr4-128 340.00 ( 0.00%) 412.00 ( -21.18%)
> Min free-odr4-256 339.00 ( 0.00%) 329.00 ( 2.95%)
> Min free-odr4-512 361.00 ( 0.00%) 409.00 ( -13.30%)
> Min free-odr4-1024 300.00 ( 0.00%) 361.00 ( -20.33%)
> Stddev alloc-odr4-1 7.29 ( 0.00%) 90.78 (-1146.00%)
> Stddev alloc-odr4-2 3.87 ( 0.00%) 51.30 (-1225.75%)
> Stddev alloc-odr4-4 3.20 ( 0.00%) 50.90 (-1491.24%)
> Stddev alloc-odr4-8 4.67 ( 0.00%) 52.23 (-1019.35%)
> Stddev alloc-odr4-16 5.72 ( 0.00%) 27.53 (-381.04%)
> Stddev alloc-odr4-32 6.25 ( 0.00%) 641.23 (-10154.46%)
> Stddev alloc-odr4-64 2.06 ( 0.00%) 386.99 (-18714.22%)
> Stddev alloc-odr4-128 14.36 ( 0.00%) 52.39 (-264.77%)
> Stddev alloc-odr4-256 32.42 ( 0.00%) 326.19 (-906.05%)
> Stddev alloc-odr4-512 65.58 ( 0.00%) 184.49 (-181.31%)
> Stddev alloc-odr4-1024 8.88 ( 0.00%) 153.01 (-1622.67%)
> Stddev free-odr4-1 2.29 ( 0.00%) 152.27 (-6549.85%)
> Stddev free-odr4-2 10.99 ( 0.00%) 73.10 (-564.89%)
> Stddev free-odr4-4 1.99 ( 0.00%) 28.40 (-1324.45%)
> Stddev free-odr4-8 2.51 ( 0.00%) 52.93 (-2007.64%)
> Stddev free-odr4-16 2.85 ( 0.00%) 26.04 (-814.88%)
> Stddev free-odr4-32 4.04 ( 0.00%) 27.05 (-569.79%)
> Stddev free-odr4-64 2.10 ( 0.00%) 48.07 (-2185.66%)
> Stddev free-odr4-128 2.63 ( 0.00%) 26.23 (-897.86%)
> Stddev free-odr4-256 6.29 ( 0.00%) 37.04 (-488.71%)
> Stddev free-odr4-512 2.56 ( 0.00%) 10.65 (-315.28%)
> Stddev free-odr4-1024 0.95 ( 0.00%) 6.46 (-582.22%)
> Max alloc-odr4-1 8564.00 ( 0.00%) 9099.00 ( -6.25%)
> Max alloc-odr4-2 6511.00 ( 0.00%) 6844.00 ( -5.11%)
> Max alloc-odr4-4 5549.00 ( 0.00%) 6038.00 ( -8.81%)
> Max alloc-odr4-8 5045.00 ( 0.00%) 5551.00 ( -10.03%)
> Max alloc-odr4-16 4800.00 ( 0.00%) 5257.00 ( -9.52%)
> Max alloc-odr4-32 5861.00 ( 0.00%) 8115.00 ( -38.46%)
> Max alloc-odr4-64 6571.00 ( 0.00%) 8292.00 ( -26.19%)
> Max alloc-odr4-128 6930.00 ( 0.00%) 8081.00 ( -16.61%)
> Max alloc-odr4-256 7372.00 ( 0.00%) 9150.00 ( -24.12%)
> Max alloc-odr4-512 10333.00 ( 0.00%) 12636.00 ( -22.29%)
> Max alloc-odr4-1024 11035.00 ( 0.00%) 12590.00 ( -14.09%)
> Max free-odr4-1 828.00 ( 0.00%) 1724.00 (-108.21%)
> Max free-odr4-2 543.00 ( 0.00%) 1192.00 (-119.52%)
> Max free-odr4-4 354.00 ( 0.00%) 519.00 ( -46.61%)
> Max free-odr4-8 293.00 ( 0.00%) 617.00 (-110.58%)
> Max free-odr4-16 260.00 ( 0.00%) 483.00 ( -85.77%)
> Max free-odr4-32 308.00 ( 0.00%) 488.00 ( -58.44%)
> Max free-odr4-64 341.00 ( 0.00%) 505.00 ( -48.09%)
> Max free-odr4-128 346.00 ( 0.00%) 497.00 ( -43.64%)
> Max free-odr4-256 353.00 ( 0.00%) 463.00 ( -31.16%)
> Max free-odr4-512 367.00 ( 0.00%) 442.00 ( -20.44%)
> Max free-odr4-1024 303.00 ( 0.00%) 381.00 ( -25.74%)
>
> With patch test results:
> patched patched
> no-monitor monitor
> Min alloc-odr4-1 8488.00 ( 0.00%) 8514.00 ( -0.31%)
> Min alloc-odr4-2 6551.00 ( 0.00%) 6527.00 ( 0.37%)
> Min alloc-odr4-4 5536.00 ( 0.00%) 5591.00 ( -0.99%)
> Min alloc-odr4-8 5008.00 ( 0.00%) 5098.00 ( -1.80%)
> Min alloc-odr4-16 4760.00 ( 0.00%) 4857.00 ( -2.04%)
> Min alloc-odr4-32 5827.00 ( 0.00%) 5919.00 ( -1.58%)
> Min alloc-odr4-64 6561.00 ( 0.00%) 6680.00 ( -1.81%)
> Min alloc-odr4-128 6898.00 ( 0.00%) 7014.00 ( -1.68%)
> Min alloc-odr4-256 7311.00 ( 0.00%) 7464.00 ( -2.09%)
> Min alloc-odr4-512 10181.00 ( 0.00%) 10286.00 ( -1.03%)
> Min alloc-odr4-1024 11205.00 ( 0.00%) 11725.00 ( -4.64%)
> Min free-odr4-1 789.00 ( 0.00%) 867.00 ( -9.89%)
> Min free-odr4-2 490.00 ( 0.00%) 526.00 ( -7.35%)
> Min free-odr4-4 350.00 ( 0.00%) 360.00 ( -2.86%)
> Min free-odr4-8 272.00 ( 0.00%) 287.00 ( -5.51%)
> Min free-odr4-16 247.00 ( 0.00%) 254.00 ( -2.83%)
> Min free-odr4-32 298.00 ( 0.00%) 304.00 ( -2.01%)
> Min free-odr4-64 334.00 ( 0.00%) 325.00 ( 2.69%)
> Min free-odr4-128 334.00 ( 0.00%) 329.00 ( 1.50%)
> Min free-odr4-256 336.00 ( 0.00%) 336.00 ( 0.00%)
> Min free-odr4-512 360.00 ( 0.00%) 342.00 ( 5.00%)
> Min free-odr4-1024 327.00 ( 0.00%) 355.00 ( -8.56%)
> Stddev alloc-odr4-1 5.19 ( 0.00%) 45.38 (-775.09%)
> Stddev alloc-odr4-2 6.99 ( 0.00%) 37.63 (-437.98%)
> Stddev alloc-odr4-4 3.91 ( 0.00%) 17.85 (-356.28%)
> Stddev alloc-odr4-8 5.15 ( 0.00%) 9.34 ( -81.47%)
> Stddev alloc-odr4-16 3.83 ( 0.00%) 5.34 ( -39.34%)
> Stddev alloc-odr4-32 1.96 ( 0.00%) 10.28 (-425.09%)
> Stddev alloc-odr4-64 1.32 ( 0.00%) 333.30 (-25141.39%)
> Stddev alloc-odr4-128 2.06 ( 0.00%) 7.37 (-258.28%)
> Stddev alloc-odr4-256 15.56 ( 0.00%) 113.48 (-629.25%)
> Stddev alloc-odr4-512 61.25 ( 0.00%) 165.09 (-169.53%)
> Stddev alloc-odr4-1024 18.89 ( 0.00%) 2.93 ( 84.51%)
> Stddev free-odr4-1 4.45 ( 0.00%) 40.12 (-800.98%)
> Stddev free-odr4-2 1.50 ( 0.00%) 29.30 (-1850.31%)
> Stddev free-odr4-4 1.27 ( 0.00%) 19.49 (-1439.40%)
> Stddev free-odr4-8 0.97 ( 0.00%) 8.93 (-823.07%)
> Stddev free-odr4-16 8.38 ( 0.00%) 4.51 ( 46.21%)
> Stddev free-odr4-32 3.18 ( 0.00%) 6.59 (-107.42%)
> Stddev free-odr4-64 2.40 ( 0.00%) 3.09 ( -28.50%)
> Stddev free-odr4-128 1.55 ( 0.00%) 2.53 ( -62.92%)
> Stddev free-odr4-256 0.41 ( 0.00%) 2.80 (-585.57%)
> Stddev free-odr4-512 1.60 ( 0.00%) 4.84 (-202.08%)
> Stddev free-odr4-1024 0.66 ( 0.00%) 1.19 ( -80.68%)
> Max alloc-odr4-1 8505.00 ( 0.00%) 8676.00 ( -2.01%)
> Max alloc-odr4-2 6572.00 ( 0.00%) 6651.00 ( -1.20%)
> Max alloc-odr4-4 5552.00 ( 0.00%) 5646.00 ( -1.69%)
> Max alloc-odr4-8 5024.00 ( 0.00%) 5131.00 ( -2.13%)
> Max alloc-odr4-16 4774.00 ( 0.00%) 4875.00 ( -2.12%)
> Max alloc-odr4-32 5834.00 ( 0.00%) 5950.00 ( -1.99%)
> Max alloc-odr4-64 6565.00 ( 0.00%) 7434.00 ( -13.24%)
> Max alloc-odr4-128 6907.00 ( 0.00%) 7034.00 ( -1.84%)
> Max alloc-odr4-256 7347.00 ( 0.00%) 7843.00 ( -6.75%)
> Max alloc-odr4-512 10315.00 ( 0.00%) 10866.00 ( -5.34%)
> Max alloc-odr4-1024 11278.00 ( 0.00%) 11733.00 ( -4.03%)
> Max free-odr4-1 803.00 ( 0.00%) 1009.00 ( -25.65%)
> Max free-odr4-2 495.00 ( 0.00%) 607.00 ( -22.63%)
> Max free-odr4-4 354.00 ( 0.00%) 417.00 ( -17.80%)
> Max free-odr4-8 275.00 ( 0.00%) 313.00 ( -13.82%)
> Max free-odr4-16 273.00 ( 0.00%) 272.00 ( 0.37%)
> Max free-odr4-32 309.00 ( 0.00%) 324.00 ( -4.85%)
> Max free-odr4-64 340.00 ( 0.00%) 335.00 ( 1.47%)
> Max free-odr4-128 340.00 ( 0.00%) 338.00 ( 0.59%)
> Max free-odr4-256 338.00 ( 0.00%) 346.00 ( -2.37%)
> Max free-odr4-512 364.00 ( 0.00%) 359.00 ( 1.37%)
> Max free-odr4-1024 329.00 ( 0.00%) 359.00 ( -9.12%)
>
> The main overhead is a slight increase in latency on the memory allocation
> and free paths due to additional per-migratetype counting, with
> theoretically minimal impact on overall performance.
>
> This patch series is based on v6.18-rc7
>
> Hongru Zhang (3):
> mm/page_alloc: add per-migratetype counts to buddy allocator
> mm/vmstat: get fragmentation statistics from per-migragetype count
> mm: optimize free_area_empty() check using per-migratetype counts
>
> include/linux/mmzone.h | 1 +
> mm/internal.h | 2 +-
> mm/mm_init.c | 1 +
> mm/page_alloc.c | 9 ++++++++-
> mm/vmstat.c | 30 +++++++-----------------------
> 5 files changed, 18 insertions(+), 25 deletions(-)
>
> --
> 2.43.0
>
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