linux-kernel - Re: [PATCH v2 6/7] mm, swap: remove swap slot cache

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Message-ID: <Z71lqkZfnDeLCjEx@MiWiFi-R3L-srv>
Date: Tue, 25 Feb 2025 14:39:38 +0800
From: Baoquan He <bhe@...hat.com>
To: Kairui Song <kasong@...cent.com>
Cc: linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>,
	Chris Li <chrisl@...nel.org>, Barry Song <v-songbaohua@...o.com>,
	Hugh Dickins <hughd@...gle.com>,
	Yosry Ahmed <yosryahmed@...gle.com>,
	"Huang, Ying" <ying.huang@...ux.alibaba.com>,
	Nhat Pham <nphamcs@...il.com>, Johannes Weiner <hannes@...xchg.org>,
	Baolin Wang <baolin.wang@...ux.alibaba.com>,
	Kalesh Singh <kaleshsingh@...gle.com>,
	Matthew Wilcox <willy@...radead.org>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 6/7] mm, swap: remove swap slot cache

On 02/25/25 at 02:02am, Kairui Song wrote:
> From: Kairui Song <kasong@...cent.com>
> 
> Slot cache is no longer needed now, removing it and all related code.
> 
> - vm-scalability with: `usemem --init-time -O -y -x -R -31 1G`,
> 12G memory cgroup using simulated pmem as SWAP (32G pmem, 32 CPUs),
> 16 test runs for each case, measuring the total throughput:
> 
>                       Before (KB/s) (stdev)  After (KB/s) (stdev)
> Random (4K):          424907.60 (24410.78)   414745.92  (34554.78)
> Random (64K):         163308.82 (11635.72)   167314.50  (18434.99)
> Sequential (4K, !-R): 6150056.79 (103205.90) 6321469.06 (115878.16)
> 
> The performance changes are below noise level.
> 
> - Build linux kernel with make -j96, using 4K folio with 1.5G memory
> cgroup limit and 64K folio with 2G memory cgroup limit, on top of tmpfs,
> 12 test runs, measuring the system time:
> 
>                   Before (s) (stdev)  After (s) (stdev)
> make -j96 (4K):   6445.69 (61.95)     6408.80 (69.46)
> make -j96 (64K):  6841.71 (409.04)    6437.99 (435.55)
> 
> Similar to above, 64k mTHP case showed a slight improvement.
> 
> Signed-off-by: Kairui Song <kasong@...cent.com>
> ---
>  include/linux/swap.h       |   2 -
>  include/linux/swap_slots.h |  28 ----
>  mm/Makefile                |   2 +-
>  mm/swap_slots.c            | 295 -------------------------------------
>  mm/swap_state.c            |   8 +-
>  mm/swapfile.c              | 193 +++++++++---------------
>  6 files changed, 71 insertions(+), 457 deletions(-)
>  delete mode 100644 include/linux/swap_slots.h
>  delete mode 100644 mm/swap_slots.c

Reviewed-by: Baoquan He <bhe@...hat.com>