[ 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). Hugh -- 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>
