Re: [PATCH 0/3] mm/mglru: clean up isolate_folios and scan_folios for readability and clarity

On 8/20/26 12:56 PM, Barry Song (Xiaomi) wrote:
> This is a cleanup series split out from the MGLRU swappiness series [1],
> with the cleanup changes separated to make them easier to review.
> 
> Right now, isolate_folios() is quite difficult to follow:
> 
> 1. It uses for_each_evictable_type(i, swappiness) to iterate over the
> types, but i is not actually used as the type within the loop body.
> 
> 2. It uses scanned == 0 to detect whether the current reclaim type is
> exhausted, but this is not an accurate indication.
> 
> 3. It has an internal retry when no folios can be isolated after scanning
> some folios, but the retry is implemented in a way nobody can understand.
> 
> This patchset makes these behaviors explicit and much easier to follow.
> 
> Run kernel builds for several rounds in a 1 GB memcg and take the
> average build time. The patchset shows almost no performance impact,
> with a very small improvement that could simply be noise:

Just FYI:

I tested this patchset with a 3G memcg limit and a 10G zram device, 
running 'make -j32' to build kernel on my 32-core Arm machines, and got 
some performance improvement for ths sys time:
	w/o patch	w/patch
sys	1845s		1570s

>                  w/o patch   w/patch      Delta
> 
> real             109.149    108.990     -0.15%
> sys              223.213    222.592     -0.28%
> 
> pgscan_file      498,208    486,994     -2.25%
> refault_file     262,696    254,688     -3.05%
> 
> Thanks very much to Baolin and Lian for their previous reviews of the
> original RFC patchset for this part.
> 
> [1] https://lore.kernel.org/linux-mm/[email protected]/
> 
> Barry Song (Xiaomi) (2):
>    mm/mglru: improve scan_folios() exhaustion detection
>    mm/mglru: retry the same type once if isolation fails due to races
> 
> Ridong Chen (1):
>    mm/mglru: improve readability of isolate_folios()
> 
>   mm/vmscan.c | 78 ++++++++++++++++++++++++++++++++++++-----------------
>   1 file changed, 54 insertions(+), 24 deletions(-)
>