(2012/03/20 4:59), Konstantin Khlebnikov wrote: > KAMEZAWA Hiroyuki wrote: >> This is just an RFC...test is not enough yet. >> >> I know it's merge window..this post is just for sharing idea. >> >> This patch merges pc->flags and pc->mem_cgroup into a word. Then, >> memcg's overhead will be 8bytes per page(4096bytes?). >> >> Because this patch will affect all memory cgroup developers, I'd like to >> show patches before MM Summit. I think we can agree the direction to >> reduce size of page_cgroup..and finally integrate into 'struct page' >> (and remove cgroup_disable= boot option...) >> >> Patch 1/3 - introduce pc_to_mem_cgroup and hide pc->mem_cgroup >> Patch 2/3 - remove pc->mem_cgroup >> Patch 3/3 - remove memory barriers. >> >> I'm now wondering when this change should be merged.... >> > > This is cool, but maybe we should skip this temporary step and merge all this stuff into page->flags. Why we should skip and delay reduction of size of page_cgroup which is considered as very big problem ? > I think we can replace zone-id and node-id in page->flags with cumulative dynamically allocated lruvec-id, > so there will be enough space for hundred cgroups even on 32-bit systems. Where section-id is ? IIUC, now, page->section->zone/node is calculated if CONFIG_SPARSEMEM. BTW, I doubt that we can modify page->flags dynamically with multi-bit operations...using cmpxchg per each page when it's charged/uncharged/other ? > > After lru_lock splitting page to lruvec translation will be much frequently used than page to zone, > so page->zone and page->node translations can be implemented as page->lruvec->zone and page->lruvec->node. > And need to take rcu_read_lock() around page_zone() ? Thanks, -Kame -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>