Changes since v4: o Rebase on next-20151118 o Hugh pointed out a problem with private mappings of tmpfs files where smaps would show a sum of shmem object's swapped out pages and swapped out COWed pages. Fixed this by falling back to the find_get_page() approach. Patches are now layered by employing find_get_page() first, and then optimizing the non-private mappings on top (with some measurements). o Expanded commit messages. Changes since v3: o Rebase on next-20151002 o Apply (feedb)acks from Michal Hocko and Konstantin Khlebnikov (Thanks!) - drop CONFIG_SHMEM ifdefs, as it was the 2nd suggestion already - add comments about not taking i_mutex in patch 2 o Rename VmAnon/VmFile/VmShm to RssAnon/RssFile... to make it hopefully more obvious that it's a breakdown of VmRSS. Naming things sucks. Changes since v2: o Rebase on next-20150805. o This means that /proc/pid/maps has the proportional swap share (SwapPss:) field as per https://lkml.org/lkml/2015/6/15/274 It's not clear what to do with shmem here so it's 0 for now. - swapped out shmem doesn't have swap entries, so we would have to look at who else has the shmem object (partially) mapped - to be more precise we should also check if his range actually includes the offset in question, which could get rather involved - or is there some easy way I don't see? o Konstantin suggested for patch 3/4 that I drop the CONFIG_SHMEM #ifdefs I didn't see the point in going against tinyfication when the work is already done, but I can do that if more people think it's better and it would block the series. Changes since v1: o In Patch 2, rely on SHMEM_I(inode)->swapped if possible, and fallback to radix tree iterator on partially mapped shmem objects, i.e. decouple shmem swap usage determination from the page walk, for performance reasons. Thanks to Jerome and Konstantin for the tips. The downside is that mm/shmem.c had to be touched. This series is based on Jerome Marchand's [1] so let me quote the first paragraph from there: There are several shortcomings with the accounting of shared memory (sysV shm, shared anonymous mapping, mapping to a tmpfs file). The values in /proc/<pid>/status and statm don't allow to distinguish between shmem memory and a shared mapping to a regular file, even though theirs implication on memory usage are quite different: at reclaim, file mapping can be dropped or write back on disk while shmem needs a place in swap. As for shmem pages that are swapped-out or in swap cache, they aren't accounted at all. The original motivation for myself is that a customer found (IMHO rightfully) confusing that e.g. top output for process swap usage is unreliable with respect to swapped out shmem pages, which are not accounted for. The fundamental difference between private anonymous and shmem pages is that the latter has PTE's converted to pte_none, and not swapents. As such, they are not accounted to the number of swapents visible e.g. in /proc/pid/status VmSwap row. It might be theoretically possible to use swapents when swapping out shmem (without extra cost, as one has to change all mappers anyway), and on swap in only convert the swapent for the faulting process, leaving swapents in other processes until they also fault (so again no extra cost). But I don't know how many assumptions this would break, and it would be too disruptive change for a relatively small benefit. Instead, my approach is to document the limitation of VmSwap, and provide means to determine the swap usage for shmem areas for those who are interested and willing to pay the price, using /proc/pid/smaps. Because outside of ipcs, I don't think it's possible to currently to determine the usage at all. The previous patchset [1] did introduce new shmem-specific fields into smaps output, and functions to determine the values. I take a simpler approach, noting that smaps output already has a "Swap: X kB" line, where currently X == 0 always for shmem areas. I think we can just consider this a bug and provide the proper value by consulting the radix tree, as e.g. mincore_page() does. In the patch changelog I explain why this is also not perfect (and cannot be without swapents), but still arguably much better than showing a 0. The last two patches are adapted from Jerome's patchset and provide a VmRSS breakdown to RssAnon, RssFile and RssShm in /proc/pid/status. Hugh noted that this is a welcome addition, and I agree that it might help e.g. debugging process memory usage at albeit non-zero, but still rather low cost of extra per-mm counter and some page flag checks. [1] http://lwn.net/Articles/611966/ Jerome Marchand (2): mm, shmem: add internal shmem resident memory accounting mm, procfs: breakdown RSS for anon, shmem and file in /proc/pid/status Vlastimil Babka (4): mm, documentation: clarify /proc/pid/status VmSwap limitations for shmem mm, proc: account for shmem swap in /proc/pid/smaps mm, proc: reduce cost of /proc/pid/smaps for shmem mappings mm, proc: reduce cost of /proc/pid/smaps for unpopulated shmem mappings Documentation/filesystems/proc.txt | 21 ++++++++-- arch/s390/mm/pgtable.c | 5 +-- fs/proc/task_mmu.c | 70 ++++++++++++++++++++++++++++++-- include/linux/mm.h | 18 ++++++++- include/linux/mm_types.h | 7 ++-- include/linux/shmem_fs.h | 4 ++ kernel/events/uprobes.c | 2 +- mm/memory.c | 30 +++++--------- mm/oom_kill.c | 5 ++- mm/rmap.c | 12 ++---- mm/shmem.c | 81 ++++++++++++++++++++++++++++++++++++++ 11 files changed, 208 insertions(+), 47 deletions(-) -- 2.6.3 -- To unsubscribe from this list: send the line "unsubscribe linux-api" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
