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由 Yang Shi 提交于
Currently when memory usage exceeds memory cgroup limit, memory cgroup just can do sync direct reclaim. This may incur unexpected stall on some applications which are sensitive to latency. Introduce background async page reclaim mechanism, like what kswapd does. Define memcg memory usage water mark by introducing wmark_ratio interface, which is from 0 to 100 and represents percentage of max limit. The wmark_high is calculated by (max * wmark_ratio / 100), the wmark_low is (wmark_high - wmark_high >> 8), which is an empirical value. If wmark_ratio is 0, it means water mark is disabled, both wmark_low and wmark_high is max, which is the default value. If wmark_ratio is setup, when charging page, if usage is greater than wmark_high, which means the available memory of memcg is low, a work would be scheduled to do background page reclaim until memory usage is reduced to wmark_low if possible. Define a dedicated unbound workqueue for scheduling water mark reclaim works. Reviewed-by: NGavin Shan <shan.gavin@linux.alibaba.com> Reviewed-by: NXunlei Pang <xlpang@linux.alibaba.com> Signed-off-by: NYang Shi <yang.shi@linux.alibaba.com>
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