On 19.03.2017 16:18, Michal Hocko wrote:
On Fri 17-03-17 21:08:31, Gerhard Wiesinger wrote:
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?
See init_per_zone_wmark_min
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?
No, we enforce swapping if the amount of free + file pages are below the
cumulative high watermark.
(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)?
be careful because systemd started to use some controllers. You can
easily check cgroup mount points.
See below.
/proc/sys/vm/min_free_kbytes
45056
So at least 45M will be kept reserved for the system. Your data
indicated you had more memory. How does /proc/zoneinfo look like?
Btw. you seem to be using fc kernel, are there any patches applied on
top of Linus tree? Could you try to retest vanilla kernel?
System looks normally now, FYI (e.g. now permanent swapping)
free
total used free shared buff/cache
available
Mem: 349076 154112 41560 184 153404 148716
Swap: 2064380 831844 1232536
cat /proc/zoneinfo
Node 0, zone DMA
per-node stats
nr_inactive_anon 9543
nr_active_anon 22105
nr_inactive_file 9877
nr_active_file 13416
nr_unevictable 0
nr_isolated_anon 0
nr_isolated_file 0
nr_pages_scanned 0
workingset_refault 1926013
workingset_activate 707166
workingset_nodereclaim 187276
nr_anon_pages 11429
nr_mapped 6852
nr_file_pages 46772
nr_dirty 1
nr_writeback 0
nr_writeback_temp 0
nr_shmem 46
nr_shmem_hugepages 0
nr_shmem_pmdmapped 0
nr_anon_transparent_hugepages 0
nr_unstable 0
nr_vmscan_write 3319047
nr_vmscan_immediate_reclaim 32363
nr_dirtied 222115
nr_written 3537529
pages free 3110
min 27
low 33
high 39
node_scanned 0
spanned 4095
present 3998
managed 3977
nr_free_pages 3110
nr_zone_inactive_anon 18
nr_zone_active_anon 3
nr_zone_inactive_file 51
nr_zone_active_file 75
nr_zone_unevictable 0
nr_zone_write_pending 0
nr_mlock 0
nr_slab_reclaimable 214
nr_slab_unreclaimable 289
nr_page_table_pages 185
nr_kernel_stack 16
nr_bounce 0
nr_zspages 0
numa_hit 1214071
numa_miss 0
numa_foreign 0
numa_interleave 0
numa_local 1214071
numa_other 0
nr_free_cma 0
protection: (0, 306, 306, 306, 306)
pagesets
cpu: 0
count: 0
high: 0
batch: 1
vm stats threshold: 4
cpu: 1
count: 0
high: 0
batch: 1
vm stats threshold: 4
node_unreclaimable: 0
start_pfn: 1
node_inactive_ratio: 0
Node 0, zone DMA32
pages free 7921
min 546
low 682
high 818
node_scanned 0
spanned 94172
present 94172
managed 83292
nr_free_pages 7921
nr_zone_inactive_anon 9525
nr_zone_active_anon 22102
nr_zone_inactive_file 9826
nr_zone_active_file 13341
nr_zone_unevictable 0
nr_zone_write_pending 1
nr_mlock 0
nr_slab_reclaimable 5829
nr_slab_unreclaimable 8622
nr_page_table_pages 2638
nr_kernel_stack 2208
nr_bounce 0
nr_zspages 0
numa_hit 23125334
numa_miss 0
numa_foreign 0
numa_interleave 14307
numa_local 23125334
numa_other 0
nr_free_cma 0
protection: (0, 0, 0, 0, 0)
pagesets
cpu: 0
count: 17
high: 90
batch: 15
vm stats threshold: 12
cpu: 1
count: 55
high: 90
batch: 15
vm stats threshold: 12
node_unreclaimable: 0
start_pfn: 4096
node_inactive_ratio: 0
mount | grep cgroup
tmpfs on /sys/fs/cgroup type tmpfs (ro,nosuid,nodev,noexec,mode=755)
cgroup on /sys/fs/cgroup/systemd type cgroup
(rw,nosuid,nodev,noexec,relatime,xattr,release_agent=/usr/lib/systemd/systemd-cgroups-agent,name=systemd)
cgroup on /sys/fs/cgroup/blkio type cgroup
(rw,nosuid,nodev,noexec,relatime,blkio)
cgroup on /sys/fs/cgroup/cpu,cpuacct type cgroup
(rw,nosuid,nodev,noexec,relatime,cpu,cpuacct)
cgroup on /sys/fs/cgroup/cpuset type cgroup
(rw,nosuid,nodev,noexec,relatime,cpuset)
cgroup on /sys/fs/cgroup/net_cls,net_prio type cgroup
(rw,nosuid,nodev,noexec,relatime,net_cls,net_prio)
cgroup on /sys/fs/cgroup/hugetlb type cgroup
(rw,nosuid,nodev,noexec,relatime,hugetlb)
cgroup on /sys/fs/cgroup/pids type cgroup
(rw,nosuid,nodev,noexec,relatime,pids)
cgroup on /sys/fs/cgroup/memory type cgroup
(rw,nosuid,nodev,noexec,relatime,memory)
cgroup on /sys/fs/cgroup/perf_event type cgroup
(rw,nosuid,nodev,noexec,relatime,perf_event)
cgroup on /sys/fs/cgroup/devices type cgroup
(rw,nosuid,nodev,noexec,relatime,devices)
cgroup on /sys/fs/cgroup/freezer type cgroup
(rw,nosuid,nodev,noexec,relatime,freezer)
There are patches (see below), but as far as I saw nothing regarding the
issues which happen.
BTW: Does it make sense to reduce lower limit for low mem VMs? e.g.
echo "10000" > /proc/sys/vm/min_free_kbytes
Thnx.
Ciao,
Gerhard
https://koji.fedoraproject.org/koji/buildinfo?buildID=870215
## Patches needed for building this package
# build tweak for build ID magic, even for -vanilla
Patch001: kbuild-AFTER_LINK.patch
## compile fixes
# ongoing complaint, full discussion delayed until ksummit/plumbers
Patch002: 0001-iio-Use-event-header-from-kernel-tree.patch
%if !%{nopatches}
# Git trees.
# Standalone patches
# a tempory patch for QCOM hardware enablement. Will be gone by end of
2016/F-26 GA
Patch420: qcom-QDF2432-tmp-errata.patch
# http://www.spinics.net/lists/arm-kernel/msg490981.html
Patch421: geekbox-v4-device-tree-support.patch
# http://www.spinics.net/lists/linux-tegra/msg26029.html
Patch422: usb-phy-tegra-Add-38.4MHz-clock-table-entry.patch
# Fix OMAP4 (pandaboard)
Patch423: arm-revert-mmc-omap_hsmmc-Use-dma_request_chan-for-reque.patch
# Not particularly happy we don't yet have a proper upstream resolution
this is the right direction
# https://www.spinics.net/lists/arm-kernel/msg535191.html
Patch424: arm64-mm-Fix-memmap-to-be-initialized-for-the-entire-section.patch
# http://patchwork.ozlabs.org/patch/587554/
Patch425: ARM-tegra-usb-no-reset.patch
Patch426: AllWinner-net-emac.patch
# http://www.spinics.net/lists/devicetree/msg163238.html
Patch430: bcm2837-initial-support.patch
# http://www.spinics.net/lists/dri-devel/msg132235.html
Patch433:
drm-vc4-Fix-OOPSes-from-trying-to-cache-a-partially-constructed-BO..patch
# bcm283x mmc for wifi
http://www.spinics.net/lists/arm-kernel/msg567077.html
Patch434: bcm283x-mmc-bcm2835.patch
# Upstream fixes for i2c/serial/ethernet MAC addresses
Patch435: bcm283x-fixes.patch
# https://lists.freedesktop.org/archives/dri-devel/2017-February/133823.html
Patch436: vc4-fix-vblank-cursor-update-issue.patch
# http://www.spinics.net/lists/arm-kernel/msg552554.html
Patch438: arm-imx6-hummingboard2.patch
Patch460: lib-cpumask-Make-CPUMASK_OFFSTACK-usable-without-deb.patch
Patch466: input-kill-stupid-messages.patch
Patch467: die-floppy-die.patch
Patch468: no-pcspkr-modalias.patch
Patch470: silence-fbcon-logo.patch
Patch471: Kbuild-Add-an-option-to-enable-GCC-VTA.patch
Patch472: crash-driver.patch
Patch473: efi-lockdown.patch
Patch487: Add-EFI-signature-data-types.patch
Patch488: Add-an-EFI-signature-blob-parser-and-key-loader.patch
# This doesn't apply. It seems like it could be replaced by
#
https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=5ac7eace2d00eab5ae0e9fdee63e38aee6001f7c
# which has an explicit line about blacklisting
Patch489: KEYS-Add-a-system-blacklist-keyring.patch
Patch490: MODSIGN-Import-certificates-from-UEFI-Secure-Boot.patch
Patch491: MODSIGN-Support-not-importing-certs-from-db.patch
Patch493: drm-i915-hush-check-crtc-state.patch
Patch494: disable-i8042-check-on-apple-mac.patch
Patch495: lis3-improve-handling-of-null-rate.patch
Patch497: scsi-sd_revalidate_disk-prevent-NULL-ptr-deref.patch
Patch498: criu-no-expert.patch
Patch499: ath9k-rx-dma-stop-check.patch
Patch500: xen-pciback-Don-t-disable-PCI_COMMAND-on-PCI-device-.patch
Patch501: Input-synaptics-pin-3-touches-when-the-firmware-repo.patch
Patch502: firmware-Drop-WARN-from-usermodehelper_read_trylock-.patch
# Patch503: drm-i915-turn-off-wc-mmaps.patch
Patch509: MODSIGN-Don-t-try-secure-boot-if-EFI-runtime-is-disa.patch
#CVE-2016-3134 rhbz 1317383 1317384
Patch665: netfilter-x_tables-deal-with-bogus-nextoffset-values.patch
# grabbed from mailing list
Patch667:
v3-Revert-tty-serial-pl011-add-ttyAMA-for-matching-pl011-console.patch
# END OF PATCH DEFINITIONS
