> A task enters into direct page reclaim, free some memory. But sometimes > the task can't get a free page after direct page reclaim because > other tasks take them (this is quite common in a multi-task workload > in my test). This behavior will bring extra latency to the task and is > unfair. Since the task already gets penalty, we'd better give it a compensation. > If a task frees some pages from direct page reclaim, we cache one freed page, > and the task will get it soon. We only consider order 0 allocation, because > it's hard to cache order > 0 page. > > Below is a trace output when a task frees some pages in try_to_free_pages(), but > get_page_from_freelist() can't get a page in direct page reclaim. > > <...>-809 [004] 730.218991: __alloc_pages_nodemask: progress 147, order 0, pid 809, comm mmap_test > <...>-806 [001] 730.237969: __alloc_pages_nodemask: progress 147, order 0, pid 806, comm mmap_test > <...>-810 [005] 730.237971: __alloc_pages_nodemask: progress 147, order 0, pid 810, comm mmap_test > <...>-809 [004] 730.237972: __alloc_pages_nodemask: progress 147, order 0, pid 809, comm mmap_test > <...>-811 [006] 730.241409: __alloc_pages_nodemask: progress 147, order 0, pid 811, comm mmap_test > <...>-809 [004] 730.241412: __alloc_pages_nodemask: progress 147, order 0, pid 809, comm mmap_test > <...>-812 [007] 730.241435: __alloc_pages_nodemask: progress 147, order 0, pid 812, comm mmap_test > <...>-809 [004] 730.245036: __alloc_pages_nodemask: progress 147, order 0, pid 809, comm mmap_test > <...>-809 [004] 730.260360: __alloc_pages_nodemask: progress 147, order 0, pid 809, comm mmap_test > <...>-805 [000] 730.260362: __alloc_pages_nodemask: progress 147, order 0, pid 805, comm mmap_test > <...>-811 [006] 730.263877: __alloc_pages_nodemask: progress 147, order 0, pid 811, comm mmap_test As far as I remembered, two years ago, similar patches was posted. but minchan found it makes performance regression when kernbench run. http://archives.free.net.ph/message/20080905.101958.0f84e87d.ja.html -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>