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28e98022b3
Currently, there is a lot of code for detecting reparent racing using
kmemcg_id as the synchronization flag. And an intermediate table is
required to record and compare the kmemcg_id.
We can simplify this by just checking the cgroup css status, skip if
cgroup is being offlined. On the reparenting side, ensure no more
allocation is on going and no further allocation will occur by using the
XArray lock as barrier.
Combined with a O(n^2) top-down walk for the allocation, we get rid of the
intermediate table allocation completely. Despite being O(n^2), it should
be actually faster because it's not practical to have a very deep cgroup
level, and in most cases the parent cgroup should have been allocated
already.
This also avoided changing kmemcg_id before reparenting, making cgroups
have a stable index for list_lru_memcg. After this change it's possible
that a dying cgroup will see a NULL value in XArray corresponding to the
kmemcg_id, because the kmemcg_id will point to an empty slot. In such
case, just fallback to use its parent.
As a result the code is simpler, following test also showed a very slight
performance gain (12 test runs):
prepare() {
mkdir /tmp/test-fs
modprobe brd rd_nr=1 rd_size=16777216
mkfs.xfs -f /dev/ram0
mount -t xfs /dev/ram0 /tmp/test-fs
for i in $(seq 10000); do
seq 8000 > "/tmp/test-fs/$i"
done
mkdir -p /sys/fs/cgroup/system.slice/bench/test/1
echo +memory > /sys/fs/cgroup/system.slice/bench/cgroup.subtree_control
echo +memory > /sys/fs/cgroup/system.slice/bench/test/cgroup.subtree_control
echo +memory > /sys/fs/cgroup/system.slice/bench/test/1/cgroup.subtree_control
echo 768M > /sys/fs/cgroup/system.slice/bench/memory.max
}
do_test() {
read_worker() {
mkdir -p "/sys/fs/cgroup/system.slice/bench/test/1/$1"
echo $BASHPID > "/sys/fs/cgroup/system.slice/bench/test/1/$1/cgroup.procs"
read -r __TMP < "/tmp/test-fs/$1";
}
read_in_all() {
for i in $(seq 10000); do
read_worker "$i" &
done; wait
}
echo 3 > /proc/sys/vm/drop_caches
time read_in_all
for i in $(seq 1 10000); do
rmdir "/sys/fs/cgroup/system.slice/bench/test/1/$i" &>/dev/null
done
}
Before:
real 0m3.498s user 0m11.037s sys 0m35.872s
real 1m33.860s user 0m11.593s sys 3m1.169s
real 1m31.883s user 0m11.265s sys 2m59.198s
real 1m32.394s user 0m11.294s sys 3m1.616s
real 1m31.017s user 0m11.379s sys 3m1.349s
real 1m31.931s user 0m11.295s sys 2m59.863s
real 1m32.758s user 0m11.254s sys 2m59.538s
real 1m35.198s user 0m11.145s sys 3m1.123s
real 1m30.531s user 0m11.393s sys 2m58.089s
real 1m31.142s user 0m11.333s sys 3m0.549s
After:
real 0m3.489s user 0m10.943s sys 0m36.036s
real 1m10.893s user 0m11.495s sys 2m38.545s
real 1m29.129s user 0m11.382s sys 3m1.601s
real 1m29.944s user 0m11.494s sys 3m1.575s
real 1m31.208s user 0m11.451s sys 2m59.693s
real 1m25.944s user 0m11.327s sys 2m56.394s
real 1m28.599s user 0m11.312s sys 3m0.162s
real 1m26.746s user 0m11.538s sys 2m55.462s
real 1m30.668s user 0m11.475s sys 3m2.075s
real 1m29.258s user 0m11.292s sys 3m0.780s
Which is slightly faster in real time.
Link: https://lkml.kernel.org/r/20241104175257.60853-5-ryncsn@gmail.com
Signed-off-by: Kairui Song <kasong@tencent.com>
Cc: Chengming Zhou <zhouchengming@bytedance.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Qi Zheng <zhengqi.arch@bytedance.com>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Shakeel Butt <shakeel.butt@linux.dev>
Cc: Waiman Long <longman@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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||
|---|---|---|
| .. | ||
| damon | ||
| kasan | ||
| kfence | ||
| kmsan | ||
| backing-dev.c | ||
| balloon_compaction.c | ||
| bootmem_info.c | ||
| cma_debug.c | ||
| cma_sysfs.c | ||
| cma.c | ||
| cma.h | ||
| compaction.c | ||
| debug_page_alloc.c | ||
| debug_page_ref.c | ||
| debug_vm_pgtable.c | ||
| debug.c | ||
| dmapool_test.c | ||
| dmapool.c | ||
| early_ioremap.c | ||
| execmem.c | ||
| fadvise.c | ||
| fail_page_alloc.c | ||
| failslab.c | ||
| filemap.c | ||
| folio-compat.c | ||
| gup_test.c | ||
| gup_test.h | ||
| gup.c | ||
| highmem.c | ||
| hmm.c | ||
| huge_memory.c | ||
| hugetlb_cgroup.c | ||
| hugetlb_vmemmap.c | ||
| hugetlb_vmemmap.h | ||
| hugetlb.c | ||
| hwpoison-inject.c | ||
| init-mm.c | ||
| internal.h | ||
| interval_tree.c | ||
| io-mapping.c | ||
| ioremap.c | ||
| Kconfig | ||
| Kconfig.debug | ||
| khugepaged.c | ||
| kmemleak.c | ||
| ksm.c | ||
| list_lru.c | ||
| maccess.c | ||
| madvise.c | ||
| Makefile | ||
| mapping_dirty_helpers.c | ||
| memblock.c | ||
| memcontrol-v1.c | ||
| memcontrol-v1.h | ||
| memcontrol.c | ||
| memfd.c | ||
| memory_hotplug.c | ||
| memory-failure.c | ||
| memory-tiers.c | ||
| memory.c | ||
| mempolicy.c | ||
| mempool.c | ||
| memremap.c | ||
| memtest.c | ||
| migrate_device.c | ||
| migrate.c | ||
| mincore.c | ||
| mlock.c | ||
| mm_init.c | ||
| mm_slot.h | ||
| mmap_lock.c | ||
| mmap.c | ||
| mmu_gather.c | ||
| mmu_notifier.c | ||
| mmzone.c | ||
| mprotect.c | ||
| mremap.c | ||
| mseal.c | ||
| msync.c | ||
| nommu.c | ||
| numa_emulation.c | ||
| numa_memblks.c | ||
| numa.c | ||
| oom_kill.c | ||
| page_alloc.c | ||
| page_counter.c | ||
| page_ext.c | ||
| page_idle.c | ||
| page_io.c | ||
| page_isolation.c | ||
| page_owner.c | ||
| page_poison.c | ||
| page_reporting.c | ||
| page_reporting.h | ||
| page_table_check.c | ||
| page_vma_mapped.c | ||
| page-writeback.c | ||
| pagewalk.c | ||
| percpu-internal.h | ||
| percpu-km.c | ||
| percpu-stats.c | ||
| percpu-vm.c | ||
| percpu.c | ||
| pgalloc-track.h | ||
| pgtable-generic.c | ||
| process_vm_access.c | ||
| ptdump.c | ||
| readahead.c | ||
| rmap.c | ||
| rodata_test.c | ||
| secretmem.c | ||
| shmem_quota.c | ||
| shmem.c | ||
| show_mem.c | ||
| shrinker_debug.c | ||
| shrinker.c | ||
| shuffle.c | ||
| shuffle.h | ||
| slab_common.c | ||
| slab.h | ||
| slub.c | ||
| sparse-vmemmap.c | ||
| sparse.c | ||
| swap_cgroup.c | ||
| swap_slots.c | ||
| swap_state.c | ||
| swap.c | ||
| swap.h | ||
| swapfile.c | ||
| truncate.c | ||
| usercopy.c | ||
| userfaultfd.c | ||
| util.c | ||
| vma_internal.h | ||
| vma.c | ||
| vma.h | ||
| vmalloc.c | ||
| vmpressure.c | ||
| vmscan.c | ||
| vmstat.c | ||
| workingset.c | ||
| z3fold.c | ||
| zbud.c | ||
| zpool.c | ||
| zsmalloc.c | ||
| zswap.c | ||