Changes in v2: - Change swap_zswap_tree() to static inline function. - Collect Acked-by tags. - Link to v1: https://lore.kernel.org/r/20240117-b4-zswap-lock-optimize-v1-0-23f6effe5775@xxxxxxxxxxxxx When testing the zswap performance by using kernel build -j32 in a tmpfs directory, I found the scalability of zswap rb-tree is not good, which is protected by the only spinlock. That would cause heavy lock contention if multiple tasks zswap_store/load concurrently. So a simple solution is to split the only one zswap rb-tree into multiple rb-trees, each corresponds to SWAP_ADDRESS_SPACE_PAGES (64M). This idea is from the commit 4b3ef9daa4fc ("mm/swap: split swap cache into 64MB trunks"). Although this method can't solve the spinlock contention completely, it can mitigate much of that contention. Below is the results of kernel build in tmpfs with zswap shrinker enabled: linux-next zswap-lock-optimize real 1m9.181s 1m3.820s user 17m44.036s 17m40.100s sys 7m37.297s 4m54.622s So there are clearly improvements. And it's complementary with the ongoing zswap xarray conversion by Chris. Anyway, I think we can also merge this first, it's complementary IMHO. So I just refresh and resend this for further discussion. Thanks for review and comment! Signed-off-by: Chengming Zhou <zhouchengming@xxxxxxxxxxxxx> --- Chengming Zhou (2): mm/zswap: make sure each swapfile always have zswap rb-tree mm/zswap: split zswap rb-tree include/linux/zswap.h | 7 +++-- mm/swapfile.c | 10 +++++-- mm/zswap.c | 76 +++++++++++++++++++++++++++++++++------------------ 3 files changed, 61 insertions(+), 32 deletions(-) --- base-commit: ab27740f76654ed58dd32ac0ba0031c18a6dea3b change-id: 20240117-b4-zswap-lock-optimize-44e071c13427 Best regards, -- Chengming Zhou <zhouchengming@xxxxxxxxxxxxx>
