On 9/24/19 9:48 AM, Michal Hocko wrote: > On Mon 23-09-19 21:31:53, Andrew Morton wrote: >> On Mon, 23 Sep 2019 17:55:24 -0700 Linus Torvalds >> <torvalds@xxxxxxxxxxxxxxxxxxxx> wrote: >> >>> On Mon, Sep 23, 2019 at 3:31 PM Andrew Morton >>> <akpm@xxxxxxxxxxxxxxxxxxxx> wrote: >>>> >>>> - almost all of -mm, as below. >>> >>> I was hoping that we could at least test the THP locality thing? >>> Is it in your queue at all, or am I supposed to just do it >>> myself? >>> >> >> Confused. I saw a privately emailed patch from David which nobody >> seems to have tested yet. I parked that for consideration after >> -rc1. Or are you referring to something else? >> >> This thing keeps stalling. It would be nice to push this along and >> get something nailed down which we can at least get into 5.4-rc, >> perhaps with a backport-this tag? > > The patch proposed by David is really non trivial wrt. potential > side effects. I have provided my review feedback [1] and it didn't > get any reaction. I really believe that we need to debug this > properly. A reproducer would be useful for others to work on that. > > There is a more fundamental problem here and we need to address it > rather than to duck tape it and whack a mole afterwards. I believe we found a problem when investigating over-reclaim in this thread [1] where it seems madvised THP allocation attempt can result in 4MB reclaimed, if there is a small zone such as ZONE_DMA on the node. As it happens, the patch "[patch 090/134] mm, reclaim: make should_continue_reclaim perform dryrun detection" in Andrew's pile should change this 4MB to 32 pages reclaimed (as a side-effect), but that has to be tested. I'm also working on a patch to not reclaim even those few pages. Of course there might be more fundamental issues with reclaim/compaction interaction, but this one seems to become hopefully clear now. [1] https://lore.kernel.org/linux-mm/4b4ba042-3741-7b16-2292-198c569da2aa@xxxxxxxxxxxx/ > [1] http://lkml.kernel.org/r/20190909193020.GD2063@xxxxxxxxxxxxxx >
