On Wed, Nov 9, 2011 at 2:44 PM, Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> wrote: > > On Fri, 4 Nov 2011 17:15:21 +0800 > Wanlong Gao <gaowanlong@xxxxxxxxxxxxxx> wrote: > > > Pagefault count has added to memcg stats since commit 456f998e, > > but forgot to doc it. > > > > Signed-off-by: Wanlong Gao <gaowanlong@xxxxxxxxxxxxxx> > > --- > > Documentation/cgroups/memory.txt | 7 +++++++ > > 1 files changed, 7 insertions(+), 0 deletions(-) > > > > diff --git a/Documentation/cgroups/memory.txt b/Documentation/cgroups/memory.txt > > index cc0ebc5..081f4f44 100644 > > --- a/Documentation/cgroups/memory.txt > > +++ b/Documentation/cgroups/memory.txt > > @@ -389,6 +389,13 @@ mapped_file - # of bytes of mapped file (includes tmpfs/shmem) > > pgpgin - # of pages paged in (equivalent to # of charging events). > > pgpgout - # of pages paged out (equivalent to # of uncharging events). > > swap - # of bytes of swap usage > > + > > +pgfault - # of page-faults > > +pgmajfault - # of major page-faults > > + These two are different from "pgpgin"/"pgpgout" stat which > > + count number of pages charged/discharged to the cgroup and > > + have no meaning of reading/writing page to disk. > > + > > inactive_anon - # of bytes of anonymous memory and swap cache memory on > > OK, but the documentation was already rather poor. > > For a start, what do pgpgin and pgpgout actually count? How about > > pgpgin: the number of pages read from disk as a result of pagefault > activity within this memcg (swapin and mapped-file pagein). Does not > include other causes of disk I/O such as read(). > > pgpgout: the number of pages written to disk as a result of swap and > mapped-file activity within this memcg. Does not include other causes > of disk I/O such as write(). > > (I'm really not sure if this is correct!) Andrew, I am afraid those two stats in memcg world have different perspective than the ones in vmstat. They are only incremented/decremented during charge/uncharge, which is regardless of having IO involved. The existing documentation isn't that clear i agree. How about: pgpgin - # of 4k page charging events to the memory cgroup pgpgout - # of 4k page uncharging events to the memory cgroup --Ying > > What are the units: is it "pages" or "multiples of 4k"? If the latter > then userspace must go off and work out what pagesize the kernel is, > which is a bit ugly and is just asking for people to develop > monitoring tools which report wrong results on other-than-4k-pagesize > setups. > > > Once we have that settled then we can move on to documenting pgfault > and pgmajfault. What are the units? Exactly which kernel actions lead > to these counters being altered? > -- To unsubscribe from this list: send the line "unsubscribe cgroups" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
