On Mon, 5 Dec 2011 16:13:06 -0800 (PST) Hugh Dickins <hughd@xxxxxxxxxx> wrote: > On Mon, 5 Dec 2011, KAMEZAWA Hiroyuki wrote: > > On Fri, 2 Dec 2011 13:08:49 +0100 > > Johannes Weiner <hannes@xxxxxxxxxxx> wrote: > > > On Fri, Dec 02, 2011 at 07:06:22PM +0900, KAMEZAWA Hiroyuki wrote: > > Hmm. IMHO, we have 2 easy ways. > > > > - Ignore PCG_USED bit at LRU handling. > > 2 problems. > > 1. memory.stat may show very wrong statistics if swapin is too often. > > 2. need careful use of mem_cgroup_charge_lrucare(). > > > > - Clear pc->mem_cgroup at swapin-readahead. > > A problem. > > 1. we need a new hook. > > > > I'll try to clear pc->mem_cgroup at swapin. > > > > Thank you for pointing out. > > Ying and I found PageCgroupAcctLRU very hard to grasp, even despite > the comments Hannes added to explain it. Now, I don't think it's difficult. It seems no file system codes add pages to LRU before add_to_page_cache() (I checked.) So, what we need to care is only swap-cache. In swap-cache path, we can do slow work. > In moving the LRU locking > from zone to memcg, we needed to depend upon pc->mem_cgroup: that > was difficult while the interpretation of pc->mem_cgroup depended > upon two flags also; and very tricky when pages were liable to shift > underneath you from one LRU to another, as flags came and went. > So we already eliminated PageCgroupAcctLRU here. > Okay, Hm, do you see performance improvement by moving locks ? > I'm fairly happy with what we have now, and have ported it forward > to 3.2.0-rc3-next-20111202: with a few improvements on top of what > we've got internally - Hannes's remark above about "amortizing the > winnings" in the page freeing hotpath has prompted me to improve > on what we had there, needs more testing but seems good so far. > > However, I've hardly begun splitting the changes up into a series: > had intended to do so last week, but day followed day... If you'd > like to see the unpolished uncommented rollup, I can post that. > please. Anyway, I'll post my own again as output even if I stop my work there. 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>