(2014/11/04 12:14), Namhyung Kim wrote: > Hi Masami, > > On Fri, 31 Oct 2014 14:51:29 -0400, Masami Hiramatsu wrote: >> Hi, >> >> Here is a sereis of patches for enabling "event cache" feature >> to perf probe. Brendan gives me this cool idea, thanks! :) >> >> In this series, I added following options/features; >> - --output option >> We can save the probe definition command for given probe-event >> instead of setting up the local tracing/kprobe_events. >> >> - --no-inlines option >> We can avoid searching the inline functions in debuginfo. Usually >> useful with wildcards since the wildcards will hit a huge amount >> of probe-points. >> >> - $params special probe argument >> $params is expanded to function parameters only, no locally defined >> variables. This is useful for function-call tracing. >> >> - wildcard support for function name >> Wildcard support is the key feature for this idea. Now we can use >> '*foo*' for function name to define the probe-point. >> >> So by using all of them, we can make an "event cache" file on all >> functions (except for inlined functions) as below. >> >> # perf probe --max-probes=100000 --no-inlines -a '* $params' -o event.cache >> >> builds "event.cache" file in which event settings for >> all function entries, like below; >> >> p:probe/reset_early_page_tables _text+12980741 >> p:probe/copy_bootdata _text+12980830 real_mode_data=%di:u64 >> p:probe/exit_amd_microcode _text+14692680 >> p:probe/early_make_pgtable _text+12981274 address=%di:u64 >> p:probe/x86_64_start_reservations _text+12981700 real_mode_data=%di:u64 >> p:probe/x86_64_start_kernel _text+12981744 real_mode_data=%di:u64 >> p:probe/reserve_ebda_region _text+12982117 > > Does this event cache support kernel modules too? AFAIK it can have a > different address whenever loaded even on a same kernel.
Yes, for the modules perf probe uses target function symbol directly instead of _text. ---- perf probe -m xfs -o - -q -a xfs_acl_exists p:probe/xfs_acl_exists xfs:xfs_acl_exists+0 ---- >> This event.cache file will be big (but much smaller than native >> debuginfo :) ) if your kernel have many option embedded. >> Anyway, you can compress it too. >> >> # wc -l event.cache >> 33813 event.cache >> # ls -sh event.cache >> 2.3M event.cache >> # ls -sh event.cache.gz >> 464K event.cache.gz >> >> For setting up a probe event, you can grep the function name >> and write it to tracing/kprobe_events, as below; >> >> # zcat event.cache.gz | \ >> grep probe/vfs_symlink > /sys/kernel/debug/tracing/kprobe_events >> >> This can be applied for the remote machine only if the machine >> runs on completely same kernel binary. Perhaps, we need some >> helper tool to check it. > > While it's useful for "agent-less" systems, I think we also need to have > a simple way to apply it with perf tools. Yeah, I see. As I've sent a reply to Arnaldo, I'd like to add --query for cached event definition by checking a build id. In that case, you just need to run perf-archive and send it to remote, then you can run perf-probe --query-set "event" on the machine. Thank you, -- Masami HIRAMATSU Software Platform Research Dept. Linux Technology Research Center Hitachi, Ltd., Yokohama Research Laboratory E-mail: masami.hiramatsu...@hitachi.com -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
