On Fri 03-03-17 16:10:27, Andrew Morton wrote: > On Thu, 2 Mar 2017 17:30:54 +0100 Michal Hocko <mhocko@xxxxxxxxxx> wrote: > > > > It's not that I think you're wrong: it *is* an implementation detail. > > > But we take a bit of incoherency from batching all over the place, so > > > it's a little odd to take a stand over this particular instance of it > > > - whether demanding that it'd be fixed, or be documented, which would > > > only suggest to users that this is special when it really isn't etc. > > > > I am not aware of other counter printed in smaps that would suffer from > > the same problem, but I haven't checked too deeply so I might be wrong. > > > > Anyway it seems that I am alone in my position so I will not insist. > > If we have any bug report then we can still fix it. > > A single lru_add_drain_all() right at the top level (in smaps_show()?) > won't kill us I do not think we want to put lru_add_drain_all cost to a random process reading /proc/<pid>/smaps. If anything the one which does the madvise should be doing this. > and should significantly improve this issue. And it > might accidentally make some of the other smaps statistics more > accurate as well. > > If not, can we please have a nice comment somewhere appropriate which > explains why LazyFree is inaccurate and why we chose to leave it that > way? Yeah, I would appreciate the comment more. What about the following --- diff --git a/Documentation/filesystems/proc.txt b/Documentation/filesystems/proc.txt index 45853e116eef..0b58b317dc76 100644 --- a/Documentation/filesystems/proc.txt +++ b/Documentation/filesystems/proc.txt @@ -444,7 +444,9 @@ a mapping associated with a file may contain anonymous pages: when MAP_PRIVATE and a page is modified, the file page is replaced by a private anonymous copy. "LazyFree" shows the amount of memory which is marked by madvise(MADV_FREE). The memory isn't freed immediately with madvise(). It's freed in memory -pressure if the memory is clean. +pressure if the memory is clean. Please note that the printed value might +be lower than the real value due to optimizations used in the current +implementation. If this is not desirable please file a bug report. "AnonHugePages" shows the ammount of memory backed by transparent hugepage. "ShmemPmdMapped" shows the ammount of shared (shmem/tmpfs) memory backed by huge pages. -- Michal Hocko SUSE Labs -- 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/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
