Messages in this thread | | | Date | Sun, 27 Feb 2005 22:20:40 +0100 | From | Christian Schmid <> | Subject | Re: Slowdown on high-load machines with 3000 sockets |
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Rik van Riel wrote: > On Sun, 27 Feb 2005, Rik van Riel wrote: > > >>Is it possible to detect when the write system call blocks? > > > OK, we got that on #kernelnewbies Initially the trace looks > innocent enough, but there is something interesting going on > with the VM. Something we may want to investigate... > > <Dragony> Feb 27 21:12:34 s02 kernel: Call Trace: > <Dragony> Feb 27 21:12:34 s02 kernel: [<803e1148>] io_schedule+0x28/0x40 > <Dragony> Feb 27 21:12:34 s02 kernel: [<8015ac26>] sync_buffer+0x36/0x50 > <Dragony> Feb 27 21:12:34 s02 kernel: [<803e1396>] __wait_on_bit+0x66/0x70 > <Dragony> Feb 27 21:12:34 s02 kernel: [<803e1428>] out_of_line_wait_on_bit+0x88/0x90 > <Dragony> Feb 27 21:12:34 s02 kernel: [<8015c2a5>] __bread_slow+0x65/0x90 > <Dragony> Feb 27 21:12:34 s02 kernel: [<8015c5bd>] __bread+0x3d/0x50 > <Dragony> Feb 27 21:12:34 s02 kernel: [<801dcdc7>] ext2_get_branch+0x77/0x120 > <Dragony> Feb 27 21:12:34 s02 kernel: [<801dd187>] ext2_get_block+0x77/0x3c0 > <Dragony> Feb 27 21:12:34 s02 kernel: [<8017d258>] do_mpage_readpage+0x1a8/0x4f0 > <Dragony> Feb 27 21:12:34 s02 kernel: [<8017d64f>] mpage_readpages+0xaf/0x130 > <Dragony> Feb 27 21:12:34 s02 kernel: [<80140c56>] read_pages+0xf6/0x100 > <Dragony> Feb 27 21:12:34 s02 kernel: [<80140f47>] do_page_cache_readahead+0x117/0x1a0 > <Dragony> Feb 27 21:12:34 s02 kernel: [<801411ab>] page_cache_readahead+0x1db/0x240 > <Dragony> Feb 27 21:12:34 s02 kernel: [<80139b10>] do_generic_mapping_read+0x100/0x3f0 > <Dragony> Feb 27 21:12:34 s02 kernel: [<8013a31b>] generic_file_sendfile+0x5b/0x70 > <Dragony> Feb 27 21:12:34 s02 kernel: [<8015a4b0>] do_sendfile+0x1f0/0x2c0 > > Looks like his program is doing a sendfile, which pauses > on reading things from disk. So far, so good. > > However, the big question is why the slowdowns go away > when min_free_kbytes is larger ? > > As an additional hint, Christian is using sys_readahead. > > Christian, how big are the data blocks you sys_readahead, and > how many do you have outstanding at a time ?
I am reading 800000 bytes of data as soon as there is less than 200000 data in the cache. I do assume the cache doesnt kill itself. I have 8 GB machine with 7,5 GB free for caching. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.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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