On Wed, May 31, 2017 at 8:44 PM, Hugh Dickins <hughd@xxxxxxxxxx> wrote: > [ Merging two mails into one response ] > > On Wed, 31 May 2017, Christoph Lameter wrote: >> On Tue, 30 May 2017, Hugh Dickins wrote: >> > SLUB: Unable to allocate memory on node -1, gfp=0x14000c0(GFP_KERNEL) >> > cache: pgtable-2^12, object size: 32768, buffer size: 65536, default order: 4, min order: 4 >> > pgtable-2^12 debugging increased min order, use slub_debug=O to disable. >> >> > I did try booting with slub_debug=O as the message suggested, but that >> > made no difference: it still hoped for but failed on order:4 allocations. >> >> I am curious as to what is going on there. Do you have the output from >> these failed allocations? > > I thought the relevant output was in my mail. I did skip the Mem-Info > dump, since that just seemed noise in this case: we know memory can get > fragmented. What more output are you looking for? > >> >> > I wanted to try removing CONFIG_SLUB_DEBUG, but didn't succeed in that: >> > it seemed to be a hard requirement for something, but I didn't find what. >> >> CONFIG_SLUB_DEBUG does not enable debugging. It only includes the code to >> be able to enable it at runtime. > > Yes, I thought so. > >> >> > I did try CONFIG_SLAB=y instead of SLUB: that lowers these allocations to >> > the expected order:3, which then results in OOM-killing rather than direct >> > allocation failure, because of the PAGE_ALLOC_COSTLY_ORDER 3 cutoff. But >> > makes no real difference to the outcome: swapping loads still abort early. >> >> SLAB uses order 3 and SLUB order 4??? That needs to be tracked down. >> >> Ahh. Ok debugging increased the object size to an order 4. This should be >> order 3 without debugging. > > But it was still order 4 when booted with slub_debug=O, which surprised me. > And that surprises you too? If so, then we ought to dig into it further. > >> >> Why are the slab allocators used to create slab caches for large object >> sizes? > > There may be more optimal ways to allocate, but I expect that when > the ppc guys are writing the code to handle both 4k and 64k page sizes, > kmem caches offer the best span of possibility without complication. > >> >> > Relying on order:3 or order:4 allocations is just too optimistic: ppc64 >> > with 4k pages would do better not to expect to support a 128TB userspace. >> >> I thought you had these huge 64k page sizes? > > ppc64 does support 64k page sizes, and they've been the default for years; > but since 4k pages are still supported, I choose to use those (I doubt > I could ever get the same load going with 64k pages). 4k is pretty much required on ppc64 when it comes to nouveau: https://bugs.freedesktop.org/show_bug.cgi?id=94757 2cts -- 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>
