On Mon, 10 Apr 2017 19:07:14 +0100 Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx> wrote: > On Mon, Apr 10, 2017 at 12:49:40PM -0500, Zi Yan wrote: > > On 10 Apr 2017, at 12:20, Mel Gorman wrote: > > > > > On Mon, Apr 10, 2017 at 11:45:08AM -0500, Zi Yan wrote: > > >>> While this could be fixed with heavy locking, it's only necessary to > > >>> make a copy of the PMD on the stack during change_pmd_range and avoid > > >>> races. A new helper is created for this as the check if quite subtle and the > > >>> existing similar helpful is not suitable. This passed 154 hours of testing > > >>> (usually triggers between 20 minutes and 24 hours) without detecting bad > > >>> PMDs or corruption. A basic test of an autonuma-intensive workload showed > > >>> no significant change in behaviour. > > >>> > > >>> Signed-off-by: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx> > > >>> Cc: stable@xxxxxxxxxxxxxxx > > >> > > >> Does this patch fix the same problem fixed by Kirill's patch here? > > >> https://lkml.org/lkml/2017/3/2/347 > > >> > > > > > > I don't think so. The race I'm concerned with is due to locks not being > > > held and is in a different path. > > > > I do not agree. Kirill's patch is fixing the same race problem but in > > zap_pmd_range(). > > > > The original autoNUMA code first clears PMD then sets it to protnone entry. > > pmd_trans_huge() does not return TRUE because it saw cleared PMD, but > > pmd_none_or_clear_bad() later saw the protnone entry and reported it as bad. > > Is this the problem you are trying solve? > > > > Kirill's patch will pmdp_invalidate() the PMD entry, which keeps _PAGE_PSE bit, > > so pmd_trans_huge() will return TRUE. In this case, it also fixes > > your race problem in change_pmd_range(). > > > > Let me know if I miss anything. > > > > Ok, now I see. I think you're correct and I withdraw the patch. I have Kirrill's thp-reduce-indentation-level-in-change_huge_pmd.patch thp-fix-madv_dontneed-vs-numa-balancing-race.patch mm-drop-unused-pmdp_huge_get_and_clear_notify.patch thp-fix-madv_dontneed-vs-madv_free-race.patch thp-fix-madv_dontneed-vs-madv_free-race-fix.patch thp-fix-madv_dontneed-vs-clear-soft-dirty-race.patch scheduled for 4.12-rc1. It sounds like thp-fix-madv_dontneed-vs-madv_free-race.patch and thp-fix-madv_dontneed-vs-madv_free-race.patch need to be boosted to 4.11 and stable? -- 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>
