On Thu, 5 Sep 2019, Mike Kravetz wrote: > I don't have a specific test for this. It is somewhat common for people > to want to allocate "as many hugetlb pages as possible". Therefore, they > will try to allocate more pages than reasonable for their environment and > take what they can get. I 'tested' by simply creating some background > activity and then seeing how many hugetlb pages could be allocated. Of > course, many tries over time in a loop. > > This patch did not cause premature allocation failures in my limited testing. > The number of pages which could be allocated with and without patch were > pretty much the same. > > Do note that I tested on top of Andrew's tree which contains this series: > http://lkml.kernel.org/r/20190806014744.15446-1-mike.krav...@oracle.com > Patch 3 in that series causes allocations to fail sooner in the case of > COMPACT_DEFERRED: > http://lkml.kernel.org/r/20190806014744.15446-4-mike.krav...@oracle.com > > hugetlb allocations have the __GFP_RETRY_MAYFAIL flag set. They are willing > to retry and wait and callers are aware of this. Even though my limited > testing did not show regressions caused by this patch, I would prefer if the > quick exit did not apply to __GFP_RETRY_MAYFAIL requests.
Good! I think that is the ideal way of handling it: we can specify the preference to actually loop and retry (but still eventually fail) for hugetlb allocations specifically for this patch by testing for __GFP_RETRY_MAYFAIL. I can add that to the formal proposal of patches 3 and 4 in this series assuming we get 5.3 settled by applying the reverts in patches 1 and 2 so that we don't cause various versions of Linux to have different default and madvise allocation policies wrt NUMA.
