Messages in this thread | | | Date | Thu, 18 Mar 2010 13:35:27 +0900 | From | KAMEZAWA Hiroyuki <> | Subject | Re: [PATCH -mmotm 1/5] memcg: disable irq at page cgroup lock |
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On Thu, 18 Mar 2010 09:49:44 +0530 Balbir Singh <balbir@linux.vnet.ibm.com> wrote:
> * KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> [2010-03-18 08:54:11]: > > > On Wed, 17 Mar 2010 17:28:55 +0530 > > Balbir Singh <balbir@linux.vnet.ibm.com> wrote: > > > > > * Andrea Righi <arighi@develer.com> [2010-03-15 00:26:38]: > > > > > > > From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> > > > > > > > > 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.
Thanks, -Kame
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