From: Kairui Song <kasong@xxxxxxxxxxx> This series is rebased on latest mm-stable to avoid conflicts. This series tries to unify and clean up the swapin path, introduce minor optimization, and make both shmem swapoff make use of SWP_SYNCHRONOUS_IO flag to skip readahead and swapcache for better performance. 1. Some benchmark for dropping readahead and swapcache for shmem with ZRAM: - Single file sequence read: perf stat --repeat 20 dd if=/tmpfs/test of=/dev/null bs=1M count=8192 (/tmpfs/test is a zero filled file, using brd as swap, 4G memcg limit) Before: 22.248 +- 0.549 After: 22.021 +- 0.684 (-1.1%) - Random read stress test: fio -name=tmpfs --numjobs=16 --directory=/tmpfs \ --size=256m --ioengine=mmap --rw=randread --random_distribution=random \ --time_based --ramp_time=1m --runtime=5m --group_reporting (using brd as swap, 2G memcg limit) Before: 1818MiB/s After: 1888MiB/s (+3.85%) - Zipf biased random read stress test: fio -name=tmpfs --numjobs=16 --directory=/tmpfs \ --size=256m --ioengine=mmap --rw=randread --random_distribution=zipf:1.2 \ --time_based --ramp_time=1m --runtime=5m --group_reporting (using brd as swap, 2G memcg limit) Before: 31.1GiB/s After: 32.3GiB/s (+3.86%) Previously, shmem always used cluster readahead, it doesn't help much even for single sequence read, and for random stress tests, the performance is better without it. In reality, due to memory and swap fragmentation cluster read-head is less helpful for ZRAM. 2. Micro benchmark which use madvise to swap out 10G zero-filled data to ZRAM then read them in, shows a performance gain for swapin path: Before: 11143285 us After: 10692644 us (+4.1%) 3. Swap off an 10G ZRAM: Before: time swapoff /dev/zram0 real 0m12.337s user 0m0.001s sys 0m12.329s After: time swapoff /dev/zram0 real 0m9.728s user 0m0.001s sys 0m9.719s This also clean up the path to apply a per swap device readahead policy for all swapin paths. V1: https://lkml.org/lkml/2023/11/19/296 Update from V1: - Rebased based on mm-unstable. - Remove behaviour changing patches, will submit in seperate series later. - Code style, naming and comments updates. - Thanks to Chris Li for very detailed and helpful review of V1. Thanks to Matthew Wilcox and Huang Ying for helpful suggestions. Kairui Song (9): mm/swapfile.c: add back some comment mm/swap: move no readahead swapin code to a stand-alone helper mm/swap: avoid doing extra unlock error checks for direct swapin mm/swap: always account swapped in page into current memcg mm/swap: introduce swapin_entry for unified readahead policy mm/swap: also handle swapcache lookup in swapin_entry mm/swap: avoid a duplicated swap cache lookup for SWP_SYNCHRONOUS_IO mm/swap: introduce a helper for swapin without vmfault swap, shmem: use new swapin helper and skip readahead conditionally mm/memory.c | 74 +++++++------------------- mm/shmem.c | 67 +++++++++++------------ mm/swap.h | 39 ++++++++++---- mm/swap_state.c | 138 +++++++++++++++++++++++++++++++++++++++++------- mm/swapfile.c | 32 +++++------ 5 files changed, 218 insertions(+), 132 deletions(-) -- 2.43.0
