On Thu, 7 Oct 2010 16:14:54 -0700 Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> wrote: > On Thu, 7 Oct 2010 17:04:05 +0900 > KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx> wrote: > > > Now, at task migration among cgroup, memory cgroup scans page table and moving > > account if flags are properly set. > > > > The core code, mem_cgroup_move_charge_pte_range() does > > > > pte_offset_map_lock(); > > for all ptes in a page table: > > 1. look into page table, find_and_get a page > > 2. remove it from LRU. > > 3. move charge. > > 4. putback to LRU. put_page() > > pte_offset_map_unlock(); > > > > for pte entries on a 3rd level? page table. > > > > This pte_offset_map_lock seems a bit long. This patch modifies a rountine as > > > > for 32 pages: pte_offset_map_lock() > > find_and_get a page > > record it > > pte_offset_map_unlock() > > for all recorded pages > > isolate it from LRU. > > move charge > > putback to LRU > > for all recorded pages > > put_page() > > The patch makes the code larger, more complex and slower! > Before this patch: text data bss dec hex filename 27163 11782 4100 43045 a825 mm/memcontrol.o After this patch: text data bss dec hex filename 27307 12294 4100 43701 aab5 mm/memcontrol.o hmm, allocating mc.target[] statically might be bad, but I'm now wondering whether I could allocate mc itself dynamically(I'll try). > I do think we're owed a more complete description of its benefits than > "seems a bit long". Have problems been observed? Any measurements > taken? > IIUC, this patch is necessary for "[PATCH] memcg: lock-free clear page writeback" later, but I agree we should describe it. Thanks, Daisuke Nishimura. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>