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Date: Fri, 17 Dec 2010 16:32:58 +1100 From: Nick Piggin <npiggin@...nel.dk> To: Frederic Weisbecker <fweisbec@...il.com> Cc: Nick Piggin <npiggin@...nel.dk>, Arnaldo Carvalho de Melo <acme@...hat.com>, linux-kernel@...r.kernel.org Subject: Re: buggy perf callgraph output On Thu, Dec 16, 2010 at 12:47:58PM +0100, Frederic Weisbecker wrote: > On Thu, Dec 16, 2010 at 12:02:45AM +1100, Nick Piggin wrote: > > On Wed, Dec 08, 2010 at 10:48:13PM +0100, Frederic Weisbecker wrote: > > > I can not reproduce it. Could you please try to reproduce, > > > run perf archive and send me your perf.data.tar.bz2 ? > > > > It seems to be happening all the time, just look further in > > callgraphs. > > > > This attached perf.data.bz2 looks like this, when using -g graph > > > > 15.05% dbench [kernel.kallsyms] [k] > > copy_user_generic_string > > | > > --- copy_user_generic_string > > | > > |---0.16%-- generic_file_aio_read > > | do_sync_read > > | vfs_read > > | | > > | --0.05%-- sys_pread64 > > | system_call > > | 0x7f64a60bb193 > > | > > |--0.10%-- generic_file_buffered_write > > | __generic_file_aio_write > > | generic_file_aio_write > > | do_sync_write > > | vfs_write > > | sys_pwrite64 > > | system_call > > | 0x7f64a60bb203 > > | 0xe01170 > > | > > ---0.11%-- dcache_readdir > > vfs_readdir > > sys_getdents > > system_call > > 0x7f64a60ade65 > > > > See, the last element is greater than the second last. > > > > -g fractal looks like this: > > > > 15.05% dbench [kernel.kallsyms] [k] > > copy_user_generic_string > > | > > --- copy_user_generic_string > > | > > |---1.09%-- generic_file_aio_read > > | do_sync_read > > | vfs_read > > | | > > | |--0.55%-- sys_pread64 > > | | system_call > > | | 0x7f64a60bb193 > > | | > > | --2.19%-- sys_read > > | system_call > > | 0x7f64a60d3ea0 > > | > > |--0.69%-- generic_file_buffered_write > > | __generic_file_aio_write > > | generic_file_aio_write > > | do_sync_write > > | vfs_write > > | sys_pwrite64 > > | system_call > > | 0x7f64a60bb203 > > | 0xe01170 > > | > > |---0.72%-- dcache_readdir > > | vfs_readdir > > | sys_getdents > > | system_call > > | 0x7f64a60ade65 > > > > > > So it's totally screwy. > > > First time I see this. > > I can reproduce but differently because I miss your perf.data.tar.bz2 > that results after the "perf archive" command, then the chains are based > on addresses and not on symbols. Oh I didn't realize perf archive, noted for next time, thanks. > But I found one of these problems on your file even without the symbols: > > --- 0x8152b50e > | > |---6.54%-- 0x810e83a7 > | 0x810d8590 > | 0x810d8710 > | 0x81002cbb > | 0xa60ade65 > | > |--13.76%-- 0x810dbc9f > | | > | |--44.73%-- 0x810d1ff5 > | | | > | | |--38.87%-- 0x810d44c4 > | | | 0x810d5242 > | | | | > | | | |--82.03%-- 0x810d5f12 > | | | | 0x810cbfd7 > | | | | 0x810cc046 > | | | | 0x810cc1ff > | | | | 0x81002cbb > | | | | 0xa60d37f5 > | | | | | > | | | | |--86.66%-- 0xe01170 > | | | | | > | | | | --13.34%-- 0x6c632f73 > | | | | > | | | --17.97%-- 0x810d629f > | | | 0x810c63a3 > | | | 0x810c648b > | | | 0x81002cbb > | | | 0xa60d3cb0 > > These are not the two last on the chain so it seems to happen even more > randomly. > > I'll fix that, thanks! That would be great, thanks! It's a really awesome tool, I appreciate your effort on it. Thanks, Nick -- 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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