【随笔】Linux drop_caches

最新推荐文章于 2025-03-01 15:50:36 发布

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最新推荐文章于 2025-03-01 15:50:36 发布 · 1.2k 阅读

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本文详细介绍了Linux系统中`drop_caches`的使用，包括如何删除clean pagecache和reclaimable slab，并探讨了pagecache（磁盘文件缓存）和slab（内核对象缓存）的概念。`drop_caches`操作是瞬时且非破坏性的，但可能会导致性能问题。同时，文章提到了内存管理的LRU算法、kswapd内核线程和pdflush刷脏页机制。

本文主要参考的内核文档：https://www.kernel.org/doc/Documentation/sysctl/vm.txt

drop_caches

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drop_caches

Writing to this will cause the kernel to drop clean caches, as well as
reclaimable slab objects like dentries and inodes.  Once dropped, their
memory becomes free.

To free pagecache:
	echo 1 > /proc/sys/vm/drop_caches
To free reclaimable slab objects (includes dentries and inodes):
	echo 2 > /proc/sys/vm/drop_caches
To free slab objects and pagecache:
	echo 3 > /proc/sys/vm/drop_caches

This is a non-destructive operation and will not free any dirty objects.
To increase the number of objects freed by this operation, the user may run
`sync' prior to writing to /proc/sys/vm/drop_caches.  This will minimize the
number of dirty objects on the system and create more