Messages in this thread | | | Subject | Re: [PATCH] mm/hmm/test: destroy xa_array instead of looping | From | Ralph Campbell <> | Date | Fri, 15 May 2020 17:56:10 -0700 |
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On 5/15/20 4:15 PM, Jason Gunthorpe wrote: > On Wed, May 13, 2020 at 02:45:07PM -0700, Ralph Campbell wrote: >> The test driver uses an xa_array to store virtual to physical address >> translations for a simulated hardware device. The MMU notifier >> invalidation callback is used to keep the table consistent with the CPU >> page table and is frequently called only for a page or two. However, if >> the test process exits unexpectedly or is killed, the range can be >> [0..ULONG_MAX] in which case calling xa_erase() for every possible PFN >> results in CPU timeouts. Munmap() can result in a large range being >> invalidated but in that case, the xa_array is likely to contain entries >> that need to be invalidated. >> Check for [0..ULONG_MAX] explicitly and just destroy the whole table. >> >> Signed-off-by: Ralph Campbell <rcampbell@nvidia.com> >> >> This patch is based on Jason Gunthorpe's hmm tree and should be folded >> into the ("mm/hmm/test: add selftest driver for HMM") patch once this >> patch is reviewed, etc. >> >> lib/test_hmm.c | 6 ++++++ >> 1 file changed, 6 insertions(+) >> >> diff --git a/lib/test_hmm.c b/lib/test_hmm.c >> index 8b36c26b717b..b89852ec3c29 100644 >> +++ b/lib/test_hmm.c >> @@ -201,7 +201,13 @@ static void dmirror_do_update(struct dmirror *dmirror, unsigned long start, >> * The XArray doesn't hold references to pages since it relies on >> * the mmu notifier to clear page pointers when they become stale. >> * Therefore, it is OK to just clear the entry. >> + * However, if the entire address space is being invalidated, it >> + * takes too long to clear them one at a time so destroy the array. >> */ >> + if (start == 0 && end == ULONG_MAX) { >> + xa_destroy(&dmirror->pt); >> + return; >> + } >> for (pfn = start >> PAGE_SHIFT; pfn < (end >> PAGE_SHIFT); pfn++) >> xa_erase(&dmirror->pt, pfn); >> } > > Just use xa_for_each_range() instead of the naive loop, it already > optimizes against membership and avoids the need for the xa_destroy > hack > > Jason >
For some reason I had looked at that and rejected it but of course, it works fine. :-) Thanks!
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