(the initial posting was missing cc's, reposting) Due to the use of vmalloc area allocations and page table populations, preparing percpu areas require GFP_KERNEL and all the allocator users are expected to be able to perform GFP_KERNEL allocations. This is mostly okay but there are cases where atomic percpu allocations are necessary usually in the IO path.
Currently, blk-throttle is implementing its own ad-hoc async allocation and there are some more planned similar usages. I posted [1] percpu_pool which generalizes the percpu atomic allocation a bit but this was a bit too cumbersome especially to use with other library data structures which make use of percpu memory as a part of it. This patchset implements proper atomic allocation support in the percpu allocator. It's largely composed of two parts. The first is updates to the area allocator so that it can skip non-populated areas. The second is async filling mechanisms which try to maintain a certain level of empty populated areas. The allocator currently tries to keep the number of empty populated pages between 2 and 4. Even with fairly aggressive back-to-back allocations, this seems enough to satisfy most allocations as long as the allocation size is under a page. This patchset contains the following 13 patches. 0001-percpu-remove-the-usage-of-separate-populated-bitmap.patch 0002-percpu-remove-may_alloc-from-pcpu_get_pages.patch 0003-percpu-move-common-parts-out-of-pcpu_-de-populate_ch.patch 0004-percpu-move-region-iterations-out-of-pcpu_-de-popula.patch 0005-percpu-make-percpu-km-set-chunk-populated-bitmap-pro.patch 0006-percpu-restructure-locking.patch 0007-percpu-make-pcpu_alloc_area-capable-of-allocating-on.patch 0008-percpu-indent-the-population-block-in-pcpu_alloc.patch 0009-percpu-implement-__-alloc_percpu_gfp.patch 0010-percpu-make-sure-chunk-map-array-has-available-space.patch 0011-percpu-implmeent-pcpu_nr_empty_pop_pages-and-chunk-n.patch 0012-percpu-rename-pcpu_reclaim_work-to-pcpu_balance_work.patch 0013-percpu-implement-asynchronous-chunk-population.patch 0001-0005 are prep patches. 0006 restructures locking so that populated areas can be given out w/o grabbing the mutex. 0007-0009 implement alloc_percpu_gfp() which supports atomic allocations. 0010-0013 implement async filling mechanisms. This patchset is on top of percpu/for-3.17-fixes 849f5169097e ("percpu: perform tlb flush after pcpu_map_pages() failure") and is available in the following git branch. git://git.kernel.org/pub/scm/linux/kernel/git/tj/percpu.git review-atomic-alloc include/linux/percpu.h | 13 - mm/percpu-km.c | 16 - mm/percpu-vm.c | 162 +++------------ mm/percpu.c | 523 +++++++++++++++++++++++++++++++++++++++---------- 4 files changed, 479 insertions(+), 235 deletions(-) Thanks. -- tejun [1] http://lkml.kernel.org/g/20140718200804.gg13...@htj.dyndns.org -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/