On Thu, Sep 25, 2014 at 2:55 PM, Peter Hurley <peter@xxxxxxxxxxxxxxxxxx> wrote: > After several days uptime with a 3.16 kernel (generally running > Thunderbird, emacs, kernel builds, several Chrome tabs on multiple > desktop workspaces) I've been seeing some really extreme slowdowns. > > Mostly the slowdowns are associated with gpu-related tasks, like > opening new emacs windows, switching workspaces, laughing at internet > gifs, etc. Because this x86_64 desktop is nouveau-based, I didn't pursue > it right away -- 3.15 is the first time suspend has worked reliably. > > This week I started looking into what the slowdown was and discovered > it's happening during dma allocation through swiotlb (the cpus can do > intel iommu but I don't use it because it's not the default for most users). > > I'm still working on a bisection but each step takes 8+ hours to > validate and even then I'm no longer sure I still have the 'bad' > commit in the bisection. [edit: yup, I started over] > > I just discovered a smattering of these in my logs and only on 3.16-rc+ kernels: > Sep 25 07:57:59 thor kernel: [28786.001300] alloc_contig_range test_pages_isolated(2bf560, 2bf562) failed > > This dual-Xeon box has 10GB and sysrq Show Memory isn't showing heavy > fragmentation [1]. > > Besides Mel's page allocator changes in 3.16, another suspect commit is: > > commit b13b1d2d8692b437203de7a404c6b809d2cc4d99 > Author: Shaohua Li <shli@xxxxxxxxxx> > Date: Tue Apr 8 15:58:09 2014 +0800 > > x86/mm: In the PTE swapout page reclaim case clear the accessed bit instead of flushing the TLB > > Specifically, this statement: > > It could cause incorrect page aging and the (mistaken) reclaim of > hot pages, but the chance of that should be relatively low. > > I'm wondering if this could cause worse-case behavior with TTM? I'm > testing a revert of this on mainline 3.16-final now, with no results yet. > > Thoughts? You may also be seeing this: https://lkml.org/lkml/2014/8/8/445 Alex -- 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>