On Wed, 2016-02-24 at 18:10 -0800, Hugh Dickins via Linuxppc-dev wrote: > I've plagiarized the subject from Paulus's "Problems with THP" mail > last weekend; but my similar problems are on PowerMac G5 baremetal, > with 4kB pages, not capable of THP and no THP configured in. > > Under heavily swapping load, running kernel builds on tmpfs in limited > memory, I've been seeing random segfaults too, internal compiler errors > etc. Not easily reproduced: sometimes happens in minutes, sometimes > not for several hours. > > I tried and failed to construct a reproducer for you: my lack of a good > recipe has deterred me from reporting it, and seeing Paulus's mail on > THP gave me hope that the answer would come up in that thread; but no, > that was quickly resolved as a THP issue, since fixed. > > (Mine had appeared to be fixed in v4.5-rc4 anyway; but I guess I > just didn't try hard enough, it resurfaced on -rc5 immediately.) > > I've seen no sign of such problems on x86. And I saw no sign of such > problems on v4.4-rc8-mm1, when I included the fixes to the _PAGE_PTE > and _PAGE_SWP_SOFT_DIRTY swapoff issues we discussed back then (in > 33 hours of load, should be good enough; but did see such problems > a couple of times before including those fixes - I took them to be > a side-effect of the page flags issue, but now rather doubt that). > > The minutes or hours thing: I wonder if that indicates a missing > initialization somewhere: that can easily show up soon after booting, > but then the machine settles into a steady state of reusing the same > structures, now initialized; until much later something disturbs the > state and it has to allocate more. Sheer speculation, but I wonder. Thanks Hugh. I do run tests on G5, but obviously not rigorously enough. I kicked off a few kernel builds on mine and it survived, though once it hits swap it's almost unusably slow. I'll leave it running overnight and see if I hit anything. cheers -- 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>