Messages in this thread | | | Subject | Re: Still OOM problems with 4.9er/4.10er kernels | From | Gerhard Wiesinger <> | Date | Fri, 17 Mar 2017 21:08:31 +0100 |
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On 17.03.2017 18:13, Michal Hocko wrote: > On Fri 17-03-17 17:37:48, Gerhard Wiesinger wrote: > [...] >> Why does the kernel prefer to swapin/out and not use >> >> a.) the free memory? > It will use all the free memory up to min watermark which is set up > based on min_free_kbytes.
Makes sense, how is /proc/sys/vm/min_free_kbytes default value calculated?
> >> b.) the buffer/cache? > the memory reclaim is strongly biased towards page cache and we try to > avoid swapout as much as possible (see get_scan_count).
If I understand it correctly, swapping is preferred over dropping the cache, right. Can this behaviour be changed to prefer dropping the cache to some minimum amount? Is this also configurable in a way? (As far as I remember e.g. kernel 2.4 dropped the caches well).
> >> There is ~100M memory available but kernel swaps all the time ... >> >> Any ideas? >> >> Kernel: 4.9.14-200.fc25.x86_64 >> >> top - 17:33:43 up 28 min, 3 users, load average: 3.58, 1.67, 0.89 >> Tasks: 145 total, 4 running, 141 sleeping, 0 stopped, 0 zombie >> %Cpu(s): 19.1 us, 56.2 sy, 0.0 ni, 4.3 id, 13.4 wa, 2.0 hi, 0.3 si, 4.7 >> st >> KiB Mem : 230076 total, 61508 free, 123472 used, 45096 buff/cache >> >> procs -----------memory---------- ---swap-- -----io---- -system-- >> ------cpu----- >> r b swpd free buff cache si so bi bo in cs us sy id wa st >> 3 5 303916 60372 328 43864 27828 200 41420 236 6984 11138 11 47 6 23 14 > I am really surprised to see any reclaim at all. 26% of free memory > doesn't sound as if we should do a reclaim at all. Do you have an > unusual configuration of /proc/sys/vm/min_free_kbytes ? Or is there > anything running inside a memory cgroup with a small limit?
nothing special set regarding /proc/sys/vm/min_free_kbytes (default values), detailed config below. Regarding cgroups, none of I know. How to check (I guess nothing is set because cg* commands are not available)?
cat /etc/sysctl.d/* | grep "^vm" vm.dirty_background_ratio = 3 vm.dirty_ratio = 15 vm.overcommit_memory = 2 vm.overcommit_ratio = 80 vm.swappiness=10
find /proc/sys/vm -type f -exec echo {} \; -exec cat {} \; /proc/sys/vm/admin_reserve_kbytes 8192 /proc/sys/vm/block_dump 0 /proc/sys/vm/compact_memory cat: /proc/sys/vm/compact_memory: Permission denied /proc/sys/vm/compact_unevictable_allowed 1 /proc/sys/vm/dirty_background_bytes 0 /proc/sys/vm/dirty_background_ratio 3 /proc/sys/vm/dirty_bytes 0 /proc/sys/vm/dirty_expire_centisecs 3000 /proc/sys/vm/dirty_ratio 15 /proc/sys/vm/dirty_writeback_centisecs 500 /proc/sys/vm/dirtytime_expire_seconds 43200 /proc/sys/vm/drop_caches 0 /proc/sys/vm/extfrag_threshold 500 /proc/sys/vm/hugepages_treat_as_movable 0 /proc/sys/vm/hugetlb_shm_group 0 /proc/sys/vm/laptop_mode 0 /proc/sys/vm/legacy_va_layout 0 /proc/sys/vm/lowmem_reserve_ratio 256 256 32 1 /proc/sys/vm/max_map_count 65530 /proc/sys/vm/memory_failure_early_kill 0 /proc/sys/vm/memory_failure_recovery 1 /proc/sys/vm/min_free_kbytes 45056 /proc/sys/vm/min_slab_ratio 5 /proc/sys/vm/min_unmapped_ratio 1 /proc/sys/vm/mmap_min_addr 65536 /proc/sys/vm/mmap_rnd_bits 28 /proc/sys/vm/mmap_rnd_compat_bits 8 /proc/sys/vm/nr_hugepages 0 /proc/sys/vm/nr_hugepages_mempolicy 0 /proc/sys/vm/nr_overcommit_hugepages 0 /proc/sys/vm/nr_pdflush_threads 0 /proc/sys/vm/numa_zonelist_order default /proc/sys/vm/oom_dump_tasks 1 /proc/sys/vm/oom_kill_allocating_task 0 /proc/sys/vm/overcommit_kbytes 0 /proc/sys/vm/overcommit_memory 2 /proc/sys/vm/overcommit_ratio 80 /proc/sys/vm/page-cluster 3 /proc/sys/vm/panic_on_oom 0 /proc/sys/vm/percpu_pagelist_fraction 0 /proc/sys/vm/stat_interval 1 /proc/sys/vm/stat_refresh /proc/sys/vm/swappiness 10 /proc/sys/vm/user_reserve_kbytes 31036 /proc/sys/vm/vfs_cache_pressure 100 /proc/sys/vm/watermark_scale_factor 10 /proc/sys/vm/zone_reclaim_mode 0
Thnx.
Ciao,
Gerhard
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