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Message-id: <19B707EB-100E-4B91-9D07-1921A18139BA@sun.com> Date: Mon, 01 Feb 2010 16:01:37 -0700 From: Andreas Dilger <adilger@....com> To: Eric Sandeen <sandeen@...hat.com> Cc: paul.chavent@...c.net, linux-ext4@...r.kernel.org Subject: Re: What represent 646345728 bytes On 2010-02-01, at 15:36, Eric Sandeen wrote: > Eric Sandeen wrote: > So uninit_bg doesn't seem to help. (this was on 2.6.32-ish) >> >> some oprofiling may be in order ... > > Or stapping ... thanks to hints from the stap guys, using a modified > version of > http://sourceware.org/systemtap/examples/profiling/fntimes.stp > I printed out function times higher than avg and correlated to writes > above average from the testcase (cleaned up manually a bit): > > 1265062212927230 function ext4_mb_load_buddy well over average time > (42303 vs 2) > 1265062212927399 function ext4_mb_regular_allocator well over > average time (42476 vs 5495) > 1265062212949252 function ext4_mb_mark_diskspace_used well over > average time (21739 vs 196) > 1265062212949306 function ext4_mb_new_blocks well over average time > (64738 vs 2457) > 1265062212949647 function ext4_ext_get_blocks well over average time > (65211 vs 1106) > 1265062212949678 function ext4_get_blocks well over average time > (65357 vs 1844) > 1265062212949695 function ext4_get_block well over average time > (65479 vs 683) > 1265062212951284 function ext4_ind_direct_IO well over average time > (68891 vs 3034) > 1265062212951299 function ext4_direct_IO well over average time > (68908 vs 3046) > 1265062212951497 function ext4_file_write well over average time > (69437 vs 3590) > > 1265062212951534 size 134470144 time 69477310 avg 3601820 > > Unfortunately under ext4_mb_load_buddy is a lot of static/inlined > functions > so no more detailed info yet. > > But loading the buddy bitmap for a new group seems to be the big > hitter here - I'll keep digging, or maybe Aneesh, who groks mballoc > better than I do (I think) might have an idea. Since these are on-demand loads, one option is when the current group is ~80% full submit an async read for the next group bitmap so that it will be in memory by the next time we need it. Cheers, Andreas -- Andreas Dilger Sr. Staff Engineer, Lustre Group Sun Microsystems of Canada, Inc. -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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