Messages in this thread | | | Date | Wed, 28 Jan 2009 14:05:20 -0800 | From | "Kok, Auke" <> | Subject | Re: [PATCH] tracer for sys_open() - sreadahead |
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Frederic Weisbecker wrote: > On Tue, Jan 27, 2009 at 06:51:37PM -0200, Arnaldo Carvalho de Melo wrote: >> Em Tue, Jan 27, 2009 at 12:08:04PM -0800, Kok, Auke escreveu: >>> This tracer monitors regular file open() syscalls. This is a fast >>> and low-overhead alternative to strace, and does not allow or >>> require to be attached to every process. >>> >>> The tracer only logs succesfull calls, as those are the only ones we >>> are currently interested in, and we can determine the absolute path >>> of these files as we log. >>> >>> Signed-off-by: Auke Kok <auke-jan.h.kok@intel.com> >> <SNIP> >> >>> diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h >>> index 4d3d381..24c17d2 100644 >>> --- a/kernel/trace/trace.h >>> +++ b/kernel/trace/trace.h >>> @@ -30,6 +30,7 @@ enum trace_type { >>> TRACE_USER_STACK, >>> TRACE_HW_BRANCHES, >>> TRACE_POWER, >>> + TRACE_OPEN, >> Why not a TRACE_VFS or TRACE_SYSCALL and then multiplex there open, >> close, etc? trace_assign_type will get humongous in no time this way. > > > That's what I was about to answer too. > That would be sad to find one tracer for open, one for read, one for write... > > >> TRACE_BLK does multiplexing, as does TRACE_PROCESS that Frank just >> posted too, and I'm working on a plugin for the patch that Neil >> submitted for the socket layer that also will need an entry there for >> its tracepoints. >> >> Frederic, it seems that discussion about subtypes has to continue :-) > > > Indeed, that becomes serious :-) >
I totally agree - this tracer was purely made quick-and-dirty to get sreadahead to the next level. The in-kernel syscall trace facility is extremely potent and I don't doubt that my patch may have been found slightly absurd by some :)
In all it was not productive to write a giant trace facility just to get sreadahead one tracer type. Now that the code works and the benefit is proven, I'm happy to see if we can work on making a decent long-term non-specialistic solution.
Auke
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