On Mon, Nov 27, 2023 at 03:45:54PM -0800, Nhat Pham wrote: > Changelog: > v7: > * Added the mem_cgroup_iter_online() function to the API for the new > behavior (suggested by Andrew Morton) (patch 2) > * Fixed a missing list_lru_del -> list_lru_del_obj (patch 1) > v6: > * Rebase on top of latest mm-unstable. > * Fix/improve the in-code documentation of the new list_lru > manipulation functions (patch 1) > v5: > * Replace reference getting with an rcu_read_lock() section for > zswap lru modifications (suggested by Yosry) > * Add a new prep patch that allows mem_cgroup_iter() to return > online cgroup. > * Add a callback that updates pool->next_shrink when the cgroup is > offlined (suggested by Yosry Ahmed, Johannes Weiner) > v4: > * Rename list_lru_add to list_lru_add_obj and __list_lru_add to > list_lru_add (patch 1) (suggested by Johannes Weiner and > Yosry Ahmed) > * Some cleanups on the memcg aware LRU patch (patch 2) > (suggested by Yosry Ahmed) > * Use event interface for the new per-cgroup writeback counters. > (patch 3) (suggested by Yosry Ahmed) > * Abstract zswap's lruvec states and handling into > zswap_lruvec_state (patch 5) (suggested by Yosry Ahmed) > v3: > * Add a patch to export per-cgroup zswap writeback counters > * Add a patch to update zswap's kselftest > * Separate the new list_lru functions into its own prep patch > * Do not start from the top of the hierarchy when encounter a memcg > that is not online for the global limit zswap writeback (patch 2) > (suggested by Yosry Ahmed) > * Do not remove the swap entry from list_lru in > __read_swapcache_async() (patch 2) (suggested by Yosry Ahmed) > * Removed a redundant zswap pool getting (patch 2) > (reported by Ryan Roberts) > * Use atomic for the nr_zswap_protected (instead of lruvec's lock) > (patch 5) (suggested by Yosry Ahmed) > * Remove the per-cgroup zswap shrinker knob (patch 5) > (suggested by Yosry Ahmed) > v2: > * Fix loongarch compiler errors > * Use pool stats instead of memcg stats when !CONFIG_MEMCG_KEM > > There are currently several issues with zswap writeback: > > 1. There is only a single global LRU for zswap, making it impossible to > perform worload-specific shrinking - an memcg under memory pressure > cannot determine which pages in the pool it owns, and often ends up > writing pages from other memcgs. This issue has been previously > observed in practice and mitigated by simply disabling > memcg-initiated shrinking: > > https://lore.kernel.org/all/20230530232435.3097106-1-nphamcs@xxxxxxxxx/T/#u > > But this solution leaves a lot to be desired, as we still do not > have an avenue for an memcg to free up its own memory locked up in > the zswap pool. > > 2. We only shrink the zswap pool when the user-defined limit is hit. > This means that if we set the limit too high, cold data that are > unlikely to be used again will reside in the pool, wasting precious > memory. It is hard to predict how much zswap space will be needed > ahead of time, as this depends on the workload (specifically, on > factors such as memory access patterns and compressibility of the > memory pages). > > This patch series solves these issues by separating the global zswap > LRU into per-memcg and per-NUMA LRUs, and performs workload-specific > (i.e memcg- and NUMA-aware) zswap writeback under memory pressure. The > new shrinker does not have any parameter that must be tuned by the > user, and can be opted in or out on a per-memcg basis. > > As a proof of concept, we ran the following synthetic benchmark: > build the linux kernel in a memory-limited cgroup, and allocate some > cold data in tmpfs to see if the shrinker could write them out and > improved the overall performance. Depending on the amount of cold data > generated, we observe from 14% to 35% reduction in kernel CPU time used > in the kernel builds. > > Domenico Cerasuolo (3): > zswap: make shrinking memcg-aware > mm: memcg: add per-memcg zswap writeback stat > selftests: cgroup: update per-memcg zswap writeback selftest > > Nhat Pham (3): > list_lru: allows explicit memcg and NUMA node selection > memcontrol: add a new function to traverse online-only memcg hierarchy > zswap: shrinks zswap pool based on memory pressure > > Documentation/admin-guide/mm/zswap.rst | 7 + > drivers/android/binder_alloc.c | 7 +- > fs/dcache.c | 8 +- > fs/gfs2/quota.c | 6 +- > fs/inode.c | 4 +- > fs/nfs/nfs42xattr.c | 8 +- > fs/nfsd/filecache.c | 4 +- > fs/xfs/xfs_buf.c | 6 +- > fs/xfs/xfs_dquot.c | 2 +- > fs/xfs/xfs_qm.c | 2 +- > include/linux/list_lru.h | 54 ++- > include/linux/memcontrol.h | 18 + > include/linux/mmzone.h | 2 + > include/linux/vm_event_item.h | 1 + > include/linux/zswap.h | 27 +- > mm/list_lru.c | 48 ++- > mm/memcontrol.c | 32 +- > mm/mmzone.c | 1 + > mm/swap.h | 3 +- > mm/swap_state.c | 26 +- > mm/vmstat.c | 1 + > mm/workingset.c | 4 +- > mm/zswap.c | 426 +++++++++++++++++--- > tools/testing/selftests/cgroup/test_zswap.c | 74 ++-- > 24 files changed, 641 insertions(+), 130 deletions(-) > > > base-commit: 5cdba94229e58a39ca389ad99763af29e6b0c5a5 No regressions when booting kernel with series applied. Tested-by: Bagas Sanjaya <bagasdotme@xxxxxxxxx> -- An old man doll... just what I always wanted! - Clara
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