Linux下清理內(nèi)存和Cache方法 /proc/sys/vm/drop_caches

頻繁的文件訪問(wèn)會(huì)導(dǎo)致系統(tǒng)的Cache使用量大增

$ free -m total used free shared buffers cached Mem: 3955 3926 28 0 55 3459 -/+ buffers/cache: 411 3544 Swap: 5726 0 5726

free內(nèi)存減少到幾十兆，系統(tǒng)運(yùn)行緩慢

運(yùn)行sync將dirty的內(nèi)容寫回硬盤
$sync

通過(guò)修改proc系統(tǒng)的drop_caches清理free的cache
$echo 3 > /proc/sys/vm/drop_caches

drop_caches的詳細(xì)文檔如下：

Writing to this will cause the kernel to drop clean caches, dentries and inodes from memory, causing that memory to become free. To free pagecache: * echo 1 > /proc/sys/vm/drop_caches To free dentries and inodes: * echo 2 > /proc/sys/vm/drop_caches To free pagecache, dentries and inodes: * echo 3 > /proc/sys/vm/drop_caches As this is a non-destructive operation, and dirty objects are notfreeable, the user should run "sync" first in order to make sure allcached objects are freed. This tunable was added in 2.6.16.

修改/etc/sysctl.conf 添加如下選項(xiàng)后就不會(huì)內(nèi)存持續(xù)增加

vm.dirty_ratio = 1 vm.dirty_background_ratio=1 vm.dirty_writeback_centisecs=2 vm.dirty_expire_centisecs=3 vm.drop_caches=3 vm.swappiness =100 vm.vfs_cache_pressure=163 vm.overcommit_memory=2 vm.lowmem_reserve_ratio=32 32 8 kern.maxvnodes=3

上面的設(shè)置比較粗暴，使cache的作用基本無(wú)法發(fā)揮。需要根據(jù)機(jī)器的狀況進(jìn)行適當(dāng)?shù)恼{(diào)節(jié)尋找最佳的折衷。

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