On Thu, 19 May 2011, KAMEZAWA Hiroyuki wrote: > On Wed, 18 May 2011 11:25:48 -0700 (PDT) > Hugh Dickins <hughd@xxxxxxxxxx> wrote: > > > On Wed, 18 May 2011, Daisuke Nishimura wrote: > > > On Tue, 17 May 2011 11:24:40 -0700 (PDT) > > > Hugh Dickins <hughd@xxxxxxxxxx> wrote: > > > > > > > mem_cgroup_count_vm_event() should update the PGMAJFAULT count for the > > > > target mm, not for current mm (but of course they're usually the same). > > > > > > > hmm, why ? > > > In shmem_getpage(), we charge the page to the memcg where current mm belongs to, > > > > (In the case when it's this fault which is creating the page. > > Just as when filemap_fault() reads in the page, add_to_page_cache > > will charge it to the current->mm's memcg, yes. Arguably correct.) > > > > > so I think counting vm events of the memcg is right. > > > > It should be consistent with which task gets the maj_flt++, and > > it should be consistent with filemap_fault(), and it should be a > > subset of what's counted by mem_cgroup_count_vm_event(mm, PGFAULT). > > > > In each case, those work on target mm rather than current->mm. > > > > Hmm, I have no strong opinion on this but yes, it makes sense to account > PGMAJFLT to the process whose mm->maj_flt++. mm->maj_flt++ would be yet another story! But it's tsk->maj_flt++. > BTW, do you think memcg should > account shmem into vma->vm_mm rather than current->mm ? When vma->vm_mm > is different from current ? At get_user_pages() + MAJFLT ? If what we have at present works well enough, I don't think we should risk breaking it with a funny change like that. Is there a reason to treat shmem differently from filemap there? You can argue that if it's shm then yes, but if it's tmpfs then no. I suppose shmem.c does usually know the difference (by VM_NORESERVE), but does not export it; and I'd prefer to keep it that way. Unless we've got a real bug to fix here, let's not mess with it. Hugh -- 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/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>