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Date: Mon, 30 Jan 2012 06:31:59 +0100 From: Eric Dumazet <eric.dumazet@...il.com> To: Shaohua Li <shaohua.li@...el.com> Cc: Wu Fengguang <wfg@...ux.intel.com>, Herbert Poetzl <herbert@...hfloor.at>, Andrew Morton <akpm@...ux-foundation.org>, LKML <linux-kernel@...r.kernel.org>, Jens Axboe <axboe@...nel.dk>, Tejun Heo <tj@...nel.org> Subject: Re: Bad SSD performance with recent kernels Le lundi 30 janvier 2012 à 11:17 +0800, Shaohua Li a écrit : > 1M block size is slow, I guess it's CPU related. > > And as for the big regression with newer kernel than 2.6.38, please > check if idle=poll > helps. CPU idle dramatically impacts disk performance and even latest > cpuidle governor > doesn't help for some CPUs. > No change with idle=poll # echo 3 >/proc/sys/vm/drop_caches ;perf record dd if=/dev/sda of=/dev/null bs=2M count=2048 2048+0 enregistrements lus 2048+0 enregistrements écrits 4294967296 octets (4,3 GB) copiés, 27,6942 s, 155 MB/s [ perf record: Woken up 3 times to write data ] [ perf record: Captured and wrote 0.884 MB perf.data (~38630 samples) ] # perf report Events: 22K cycles 40,14% dd [kernel.kallsyms] [k] copy_user_generic_string 3,12% dd [kernel.kallsyms] [k] native_read_tsc 3,00% dd [kernel.kallsyms] [k] put_page 2,98% dd [kernel.kallsyms] [k] iowrite8 2,04% dd [kernel.kallsyms] [k] get_page_from_freelist 1,87% dd [kernel.kallsyms] [k] delay_tsc 1,77% dd [kernel.kallsyms] [k] kmem_cache_alloc 1,69% dd [kernel.kallsyms] [k] __mem_cgroup_commit_charge 1,52% dd [kernel.kallsyms] [k] submit_bh 1,38% dd [kernel.kallsyms] [k] ioread8 1,32% dd [kernel.kallsyms] [k] __rmqueue 1,29% dd [kernel.kallsyms] [k] block_read_full_page 1,28% dd [kernel.kallsyms] [k] __ticket_spin_lock 1,23% dd [kernel.kallsyms] [k] __slab_alloc 1,15% dd [kernel.kallsyms] [k] file_read_actor 0,85% dd [kernel.kallsyms] [k] generic_make_request.part.51 0,84% dd [kernel.kallsyms] [k] __alloc_pages_nodemask 0,82% dd [kernel.kallsyms] [k] create_empty_buffers 0,81% dd [kernel.kallsyms] [k] get_partial_node 0,81% dd [kernel.kallsyms] [k] lookup_page_cgroup 0,78% dd [kernel.kallsyms] [k] mem_cgroup_add_lru_list.part.45 0,72% dd [kernel.kallsyms] [k] ____pagevec_lru_add_fn # echo 3 >/proc/sys/vm/drop_caches ;perf record dd if=/dev/sda of=/dev/null bs=1M count=4096 4096+0 enregistrements lus 4096+0 enregistrements écrits 4294967296 octets (4,3 GB) copiés, 25,8117 s, 166 MB/s [ perf record: Woken up 3 times to write data ] [ perf record: Captured and wrote 0.810 MB perf.data (~35398 samples) ] # perf report Events: 20K cycles 31,91% dd [kernel.kallsyms] [k] copy_user_generic_string 3,87% dd [kernel.kallsyms] [k] native_read_tsc 3,58% dd [kernel.kallsyms] [k] iowrite8 2,43% dd [kernel.kallsyms] [k] put_page 2,30% dd [kernel.kallsyms] [k] delay_tsc 2,09% dd [kernel.kallsyms] [k] get_page_from_freelist 1,96% dd [kernel.kallsyms] [k] __mem_cgroup_commit_charge 1,79% dd [kernel.kallsyms] [k] submit_bh 1,75% dd [kernel.kallsyms] [k] kmem_cache_alloc 1,74% dd [kernel.kallsyms] [k] ioread8 1,68% dd [kernel.kallsyms] [k] block_read_full_page 1,62% dd [kernel.kallsyms] [k] __ticket_spin_lock 1,38% dd [kernel.kallsyms] [k] __rmqueue 1,12% dd [kernel.kallsyms] [k] create_empty_buffers 1,08% dd [kernel.kallsyms] [k] __slab_alloc 1,07% dd [kernel.kallsyms] [k] file_read_actor 1,06% dd [kernel.kallsyms] [k] generic_make_request.part.51 0,94% dd [kernel.kallsyms] [k] lookup_page_cgroup 0,85% dd [kernel.kallsyms] [k] __alloc_pages_nodemask 0,85% dd [kernel.kallsyms] [k] find_get_page 0,83% dd [kernel.kallsyms] [k] __lru_cache_add 0,81% dd [kernel.kallsyms] [k] add_to_page_cache_locked.part.29 # echo 3 >/proc/sys/vm/drop_caches ;perf record dd if=/dev/sda of=/dev/null bs=128k count=32768 32768+0 enregistrements lus 32768+0 enregistrements écrits 4294967296 octets (4,3 GB) copiés, 19,6924 s, 218 MB/s [ perf record: Woken up 3 times to write data ] [ perf record: Captured and wrote 0.961 MB perf.data (~41992 samples) ] # perf report 29,85% dd [kernel.kallsyms] [k] copy_user_generic_string 2,61% dd [kernel.kallsyms] [k] __mem_cgroup_commit_charge 2,53% dd [kernel.kallsyms] [k] get_page_from_freelist 2,27% dd [kernel.kallsyms] [k] block_read_full_page 1,99% dd [kernel.kallsyms] [k] __ticket_spin_lock 1,81% dd [kernel.kallsyms] [k] kmem_cache_alloc 1,65% dd [kernel.kallsyms] [k] file_read_actor 1,60% dd [kernel.kallsyms] [k] __rmqueue 1,58% dd [kernel.kallsyms] [k] put_page 1,51% dd [kernel.kallsyms] [k] submit_bh 1,37% dd [kernel.kallsyms] [k] create_empty_buffers 1,30% dd [kernel.kallsyms] [k] generic_make_request.part.51 1,09% dd [kernel.kallsyms] [k] __alloc_pages_nodemask 1,06% dd [kernel.kallsyms] [k] do_generic_file_read.constprop.35 1,01% dd [kernel.kallsyms] [k] lookup_page_cgroup 1,00% dd [kernel.kallsyms] [k] add_to_page_cache_locked.part.29 0,93% dd [kernel.kallsyms] [k] find_get_page 0,92% dd [kernel.kallsyms] [k] blk_rq_map_sg 0,92% dd [kernel.kallsyms] [k] radix_tree_insert 0,89% dd [kernel.kallsyms] [k] alloc_pages_current 0,88% dd [kernel.kallsyms] [k] mem_cgroup_add_lru_list.part.45 0,88% dd [kernel.kallsyms] [k] radix_tree_lookup_element -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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