From: Johannes Weiner Date: Wed, 23 Mar 2011 23:42:26 +0000 (-0700) Subject: memcg: no uncharged pages reach page_cgroup_zoneinfo X-Git-Tag: v2.6.39-rc1~161 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=ad324e94475a04cfcdfdb11ad20f8ea81268e411;p=pandora-kernel.git memcg: no uncharged pages reach page_cgroup_zoneinfo This patch series removes the direct page pointer from struct page_cgroup, which saves 20% of per-page memcg memory overhead (Fedora and Ubuntu enable memcg per default, openSUSE apparently too). The node id or section number is encoded in the remaining free bits of pc->flags which allows calculating the corresponding page without the extra pointer. I ran, what I think is, a worst-case microbenchmark that just cats a large sparse file to /dev/null, because it means that walking the LRU list on behalf of per-cgroup reclaim and looking up pages from page_cgroups is happening constantly and at a high rate. But it made no measurable difference. A profile reported a 0.11% share of the new lookup_cgroup_page() function in this benchmark. This patch: All callsites check PCG_USED before passing pc->mem_cgroup, so the latter is never NULL. Signed-off-by: Johannes Weiner Acked-by: KAMEZAWA Hiroyuki Cc: Daisuke Nishimura Acked-by: Balbir Singh Cc: Minchan Kim Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- Reading git-diff-tree failed