On Thu 05-11-20 14:15:07, Rik van Riel wrote: > The allocation flags of anonymous transparent huge pages can be controlled > through the files in /sys/kernel/mm/transparent_hugepage/defrag, which can > help the system from getting bogged down in the page reclaim and compaction > code when many THPs are getting allocated simultaneously. > > However, the gfp_mask for shmem THP allocations were not limited by those > configuration settings, and some workloads ended up with all CPUs stuck > on the LRU lock in the page reclaim code, trying to allocate dozens of > THPs simultaneously. > > This patch applies the same configurated limitation of THPs to shmem > hugepage allocations, to prevent that from happening. I believe you should also exaplain why we want to control defrag by the global knob while the enable logic is per mount. > This way a THP defrag setting of "never" or "defer+madvise" will result > in quick allocation failures without direct reclaim when no 2MB free > pages are available. > > With this patch applied, THP allocations for tmpfs will be a little > more aggressive than today for files mmapped with MADV_HUGEPAGE, > and a little less aggressive for files that are not mmapped or > mapped without that flag. This begs some numbers. A little is rather bad unit of performance. I do agree that unifying those makes sense in general though. > Signed-off-by: Rik van Riel <riel@xxxxxxxxxxx> > --- > include/linux/gfp.h | 2 ++ > mm/huge_memory.c | 6 +++--- > mm/shmem.c | 8 +++++--- > 3 files changed, 10 insertions(+), 6 deletions(-) -- Michal Hocko SUSE Labs
