On Fri 24-02-17 13:31:49, Shaohua Li wrote: > show MADV_FREE pages info of each vma in smaps. The interface is for > diganose or monitoring purpose, userspace could use it to understand > what happens in the application. Since userspace could dirty MADV_FREE > pages without notice from kernel, this interface is the only place we > can get accurate accounting info about MADV_FREE pages. I have just got to test this patchset and noticed something that was a bit surprising madvise(mmap(len), len, MADV_FREE) Size: 102400 kB Rss: 102400 kB Pss: 102400 kB Shared_Clean: 0 kB Shared_Dirty: 0 kB Private_Clean: 102400 kB Private_Dirty: 0 kB Referenced: 0 kB Anonymous: 102400 kB LazyFree: 102368 kB It took me a some time to realize that LazyFree is not accurate because there are still pages on the per-cpu lru_lazyfree_pvecs. I believe this is an implementation detail which shouldn't be visible to the userspace. Should we simply drain the pagevec? A crude way would be to simply lru_add_drain_all after we are done with the given range. We can also make this lru_lazyfree_pvecs specific but I am not sure this is worth the additional code. --- diff --git a/mm/madvise.c b/mm/madvise.c index dc5927c812d3..d2c318db16c9 100644 --- a/mm/madvise.c +++ b/mm/madvise.c @@ -474,7 +474,7 @@ static int madvise_free_single_vma(struct vm_area_struct *vma, madvise_free_page_range(&tlb, vma, start, end); mmu_notifier_invalidate_range_end(mm, start, end); tlb_finish_mmu(&tlb, start, end); - + lru_add_drain_all(); return 0; } -- 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>
