Re: [PATCH v5 00/14] mm/mglru: improve reclaim loop and dirty folio handling

[wangxinyu19 <wxy2009nrrr@163.com>]

On Mon, 13 Apr 2026 00:48:14 +0800, Kairui Song wrote:
> This series is based on mm-unstable, also applies to mm-new.
> 
> This series cleans up and slightly improves MGLRU's reclaim loop and
> dirty writeback handling. As a result, we can see an up to ~30% increase
> in some workloads like MongoDB with YCSB and a huge decrease in file
> refault, no swap involved. Other common benchmarks have no regression,
> and LOC is reduced, with less unexpected OOM, too.
> 
> Some of the problems were found in our production environment, and
> others were mostly exposed while stress testing during the development
> of the LSM/MM/BPF topic on improving MGLRU [1]. This series cleans up
> the code base and fixes several performance issues, preparing for
> further work.
> 
> MGLRU's reclaim loop is a bit complex, and hence these problems are
> somehow related to each other. The aging, scan number calculation, and
> reclaim loop are coupled together, and the dirty folio handling logic is
> quite different, making the reclaim loop hard to follow and the dirty
> flush ineffective.

> This series slightly cleans up and improves these issues using a scan
> budget by calculating the number of folios to scan at the beginning of
> the loop, and decouples aging from the reclaim calculation helpers.
> Then, move the dirty flush logic inside the reclaim loop so it can kick
> in more effectively. These issues are somehow related, and this series
> handles them and improves MGLRU reclaim in many ways.
> 
> Test results: All tests are done on a 48c96t NUMA machine with 2 nodes
> and a 128G memory machine using NVME as storage.

Hi Kairui,

We have tested this patch series on Android device under a typical scenario.

The test consisted of cold-starting multiple applications sequentially
under moderate system load (some services running on the background, 
such as map navigating, AI voice-assistant). Each test round cold-starts
a fixed set of apps one by one and records the cold start latency.
A total of 100 rounds were conducted to ensure statistical significance.

Before:
  /proc/vmstat info:
    pgpgin 269,224
    pgpgout 226,078
    workingset_refault_anon 237
    workingset_refault_file 27689

  Launch Time Summary (all apps, all runs)
    Mean 868.0ms
    P50 888.0ms
    P90 1274.2ms
    P95 1399.0ms

After:
  /proc/vmstat info:
    pgpgin 223,801                (-16.9%)
    pgpgout 308,873
    workingset_refault_anon 498
    workingset_refault_file 17075 (-38.3%)

  Launch Time Summary (all apps, all runs)
    Mean 850.5ms (-2.07%)
    P50 861.5ms  (-3.04%)
    P90 1179.0ms (-8.05%)
    P95 1228.0ms (-12.2%)
    
--
Best regards,
Xinyu