linux/Documentation
Waiman Long 04f768a39d mm, slab: extend slab/shrink to shrink all memcg caches
Currently, a value of '1" is written to /sys/kernel/slab/<slab>/shrink
file to shrink the slab by flushing out all the per-cpu slabs and free
slabs in partial lists.  This can be useful to squeeze out a bit more
memory under extreme condition as well as making the active object counts
in /proc/slabinfo more accurate.

This usually applies only to the root caches, as the SLUB_MEMCG_SYSFS_ON
option is usually not enabled and "slub_memcg_sysfs=1" not set.  Even if
memcg sysfs is turned on, it is too cumbersome and impractical to manage
all those per-memcg sysfs files in a real production system.

So there is no practical way to shrink memcg caches.  Fix this by enabling
a proper write to the shrink sysfs file of the root cache to scan all the
available memcg caches and shrink them as well.  For a non-root memcg
cache (when SLUB_MEMCG_SYSFS_ON or slub_memcg_sysfs is on), only that
cache will be shrunk when written.

On a 2-socket 64-core 256-thread arm64 system with 64k page after
a parallel kernel build, the the amount of memory occupied by slabs
before shrinking slabs were:

 # grep task_struct /proc/slabinfo
 task_struct        53137  53192   4288   61    4 : tunables    0    0
 0 : slabdata    872    872      0
 # grep "^S[lRU]" /proc/meminfo
 Slab:            3936832 kB
 SReclaimable:     399104 kB
 SUnreclaim:      3537728 kB

After shrinking slabs (by echoing "1" to all shrink files):

 # grep "^S[lRU]" /proc/meminfo
 Slab:            1356288 kB
 SReclaimable:     263296 kB
 SUnreclaim:      1092992 kB
 # grep task_struct /proc/slabinfo
 task_struct         2764   6832   4288   61    4 : tunables    0    0
 0 : slabdata    112    112      0

Link: http://lkml.kernel.org/r/20190723151445.7385-1-longman@redhat.com
Signed-off-by: Waiman Long <longman@redhat.com>
Acked-by: Roman Gushchin <guro@fb.com>
Acked-by: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2019-09-24 15:54:07 -07:00
..
ABI mm, slab: extend slab/shrink to shrink all memcg caches 2019-09-24 15:54:07 -07:00
accounting
admin-guide - crypto and DM crypt advances that allow the crypto API to reclaim 2019-09-21 10:40:37 -07:00
arm
arm64 Merge branch 'irq-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2019-09-17 11:42:15 -07:00
block docs: block: null_blk: enhance document style 2019-09-11 16:04:22 -06:00
bpf
cdrom
core-api docs: printk-formats: Stop encouraging use of unnecessary %h[xudi] and %hh[xudi] 2019-09-14 01:57:43 -06:00
cpu-freq
crypto Merge branch 'linus' of git://git.kernel.org/pub/scm/linux/kernel/git/herbert/crypto-2.6 2019-09-18 12:11:14 -07:00
dev-tools
devicetree RTC for 5.4 2019-09-22 11:05:43 -07:00
doc-guide
driver-api This is the bulk of pin control changes for the v5.4 kernel 2019-09-19 14:19:33 -07:00
EDID
fault-injection
fb
features It's a somewhat calmer cycle for docs this time, as the churn of the mass 2019-09-17 16:22:26 -07:00
filesystems f2fs-for-5.4-rc1 2019-09-21 14:26:33 -07:00
firmware_class
firmware-guide
fpga
gpu
hid
hwmon It's a somewhat calmer cycle for docs this time, as the churn of the mass 2019-09-17 16:22:26 -07:00
i2c
ia64
ide
iio
infiniband Documentation/infiniband: update name of some functions 2019-09-13 16:55:55 -03:00
input
ioctl
isdn
kbuild Modules updates for v5.4 2019-09-22 10:34:46 -07:00
kernel-hacking docs: Add documentation for Symbol Namespaces 2019-09-10 10:30:49 +02:00
leds
livepatch
locking doc🔒 remove reference to clever use of read-write lock 2019-09-14 01:53:27 -06:00
m68k
maintainer
media drm main pull for 5.4-rc1 2019-09-19 16:24:24 -07:00
mic
mips Main MIPS changes for v5.4: 2019-09-22 09:30:30 -07:00
misc-devices
netlabel
networking Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next 2019-09-18 12:34:53 -07:00
nios2
openrisc
parisc
PCI
pcmcia
power Merge branches 'pm-opp', 'pm-qos', 'acpi-pm', 'pm-domains' and 'pm-tools' 2019-09-17 09:49:19 +02:00
powerpc docs: powerpc: Add missing documentation reference 2019-09-17 23:59:34 +10:00
process It's a somewhat calmer cycle for docs this time, as the churn of the mass 2019-09-17 16:22:26 -07:00
RCU
riscv It's a somewhat calmer cycle for docs this time, as the churn of the mass 2019-09-17 16:22:26 -07:00
s390
scheduler
scsi
security It's a somewhat calmer cycle for docs this time, as the churn of the mass 2019-09-17 16:22:26 -07:00
sh
sound sound updates for 5.4 2019-09-17 17:43:33 -07:00
sparc
sphinx
sphinx-static
spi
target
timers
trace Tracing updates: 2019-09-20 11:19:48 -07:00
translations
usb
userspace-api
virt * More selftests 2019-09-11 18:06:15 +02:00
virtual
vm
w1
watchdog
x86
xtensa
.gitignore
atomic_bitops.txt
atomic_t.txt
bus-virt-phys-mapping.txt
Changes
CodingStyle
conf.py
COPYING-logo
crc32.txt
debugging-modules.txt
debugging-via-ohci1394.txt
digsig.txt
DMA-API-HOWTO.txt
DMA-API.txt
DMA-attributes.txt
DMA-ISA-LPC.txt
docutils.conf
dontdiff
futex-requeue-pi.txt
hwspinlock.txt
index.rst Main MIPS changes for v5.4: 2019-09-22 09:30:30 -07:00
io_ordering.txt
io-mapping.txt
IPMI.txt
IRQ-affinity.txt
IRQ-domain.txt
IRQ.txt
irqflags-tracing.txt
Kconfig
kobject.txt
kprobes.txt
kref.txt
logo.gif
lzo.txt
mailbox.txt
Makefile
memory-barriers.txt
nommu-mmap.txt
padata.txt padata: allocate workqueue internally 2019-09-13 21:15:39 +10:00
percpu-rw-semaphore.txt
pi-futex.txt
preempt-locking.txt
rbtree.txt
remoteproc.txt
robust-futex-ABI.txt
robust-futexes.txt
rpmsg.txt
speculation.txt
static-keys.txt
SubmittingPatches
tee.txt
this_cpu_ops.txt
unaligned-memory-access.txt
xz.txt