Messages in this thread | | | Date | Wed, 3 Dec 2014 21:49:04 -0800 | Subject | Re: frequent lockups in 3.18rc4 | From | Linus Torvalds <> |
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On Wed, Dec 3, 2014 at 7:15 PM, Chris Mason <clm@fb.com> wrote: > > One guess is that trinity is generating a huge number of tlb > invalidations over sparse and horrible ranges. Perhaps the old code was > falling back to full tlb flushes before Dave Hansen's string of fixes?
Hmm. I agree that we've had some of the backtraces look like TLB flushing might be involved. Not all, though. And I'm not seeing where a loop over up to 33 pages should matter over doing a full TLB flush.
What *might* matter is if we somehow get that number wrong, and the loops like
addr = f->flush_start; while (addr < f->flush_end) { __flush_tlb_single(addr); addr += PAGE_SIZE; }
ends up looping a *lot* due to some bug, and then the IPI itself would take so long that the watchdog could trigger.
But I do not see how that could actually happen. As far as I can tell, either the number of pages is limited to less than 33, or we have that TLB_FLUSH_ALL case.
Do you see something I don't?
Linus
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