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由 Roman Gushchin 提交于
mainline inclusion from mainline-v5.14-rc1 commit f1833241 category: bugfix bugzilla: https://gitee.com/openeuler/kernel/issues/I4BE79 CVE: NA ------------------------------------------------- From Roman ("percpu: partial chunk depopulation"): In our [Facebook] production experience the percpu memory allocator is sometimes struggling with returning the memory to the system. A typical example is a creation of several thousands memory cgroups (each has several chunks of the percpu data used for vmstats, vmevents, ref counters etc). Deletion and complete releasing of these cgroups doesn't always lead to a shrinkage of the percpu memory, so that sometimes there are several GB's of memory wasted. The underlying problem is the fragmentation: to release an underlying chunk all percpu allocations should be released first. The percpu allocator tends to top up chunks to improve the utilization. It means new small-ish allocations (e.g. percpu ref counters) are placed onto almost filled old-ish chunks, effectively pinning them in memory. This patchset solves this problem by implementing a partial depopulation of percpu chunks: chunks with many empty pages are being asynchronously depopulated and the pages are returned to the system. To illustrate the problem the following script can be used: Reviewed-by: NKefeng Wang <wangkefeng.wang@huawei.com> Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>
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