Messages in this thread | | | Date | Fri, 29 Oct 2010 19:13:00 +0800 | From | Wu Fengguang <> | Subject | Re: [PATCH v4 06/11] memcg: add dirty page accounting infrastructure |
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On Fri, Oct 29, 2010 at 03:09:09PM +0800, Greg Thelen wrote:
> + > + case MEMCG_NR_FILE_DIRTY: > + /* Use Test{Set,Clear} to only un/charge the memcg once. */ > + if (val > 0) { > + if (TestSetPageCgroupFileDirty(pc)) > + val = 0; > + } else { > + if (!TestClearPageCgroupFileDirty(pc)) > + val = 0; > + }
I'm wondering why TestSet/TestClear and even the cgroup page flags for dirty/writeback/unstable pages are necessary at all (it helps to document in changelog if there are any). For example, VFS will call TestSetPageDirty() before calling mem_cgroup_inc_page_stat(MEMCG_NR_FILE_DIRTY), so there should be no chance of false double counting.
Thanks, Fengguang
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