* KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx> [2010-03-18 13:35:27]: > On Thu, 18 Mar 2010 09:49:44 +0530 > Balbir Singh <balbir@xxxxxxxxxxxxxxxxxx> wrote: > > > * KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx> [2010-03-18 08:54:11]: > > > > > On Wed, 17 Mar 2010 17:28:55 +0530 > > > Balbir Singh <balbir@xxxxxxxxxxxxxxxxxx> wrote: > > > > > > > * Andrea Righi <arighi@xxxxxxxxxxx> [2010-03-15 00:26:38]: > > > > > > > > > From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx> > > > > > > > > > > Now, file-mapped is maintaiend. But more generic update function > > > > > will be needed for dirty page accounting. > > > > > > > > > > For accountig page status, we have to guarantee lock_page_cgroup() > > > > > will be never called under tree_lock held. > > > > > To guarantee that, we use trylock at updating status. > > > > > By this, we do fuzzy accounting, but in almost all case, it's correct. > > > > > > > > > > > > > I don't like this at all, but in almost all cases is not acceptable > > > > for statistics, since decisions will be made on them and having them > > > > incorrect is really bad. Could we do a form of deferred statistics and > > > > fix this. > > > > > > > > > > plz show your implementation which has no performance regresssion. > > > For me, I don't neee file_mapped accounting, at all. If we can remove that, > > > we can add simple migration lock. > > > > That doesn't matter, if you need it, I think the larger user base > > matters. Unmapped and mapped page cache is critical and I use it > > almost daily. > > > > > file_mapped is a feattue you added. please improve it. > > > > > > > I will, but please don't break it silently > > > Andrea, could you go in following way ? > > - don't touch FILE_MAPPED stuff. > - add new functions for other dirty accounting stuff as in this series. > (using trylock is ok.) > > Then, no probelm. It's ok to add mem_cgroup_udpate_stat() indpendent from > mem_cgroup_update_file_mapped(). The look may be messy but it's not your > fault. But please write "why add new function" to patch description. > > I'm sorry for wasting your time. Do we need to go down this route? We could check the stat and do the correct thing. In case of FILE_MAPPED, always grab page_cgroup_lock and for others potentially look at trylock. It is OK for different stats to be protected via different locks. /me takes a look at the code again. -- Three Cheers, Balbir -- 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>