Date: Sun, 23 Nov 2008 20:26:29 +0000 From: "Ray Kinsella" <raykinsella78@gmail.com> To: "Attilio Rao" <attilio@freebsd.org> Cc: FreeBSD Arch <arch@freebsd.org>, freebsd-performance@freebsd.org, Joseph Koshy <jkoshy@freebsd.org> Subject: Re: [PATCH] pmcannotate tool Message-ID: <584ec6bb0811231226x7d1b53ccgc5e28bfc297009a2@mail.gmail.com> In-Reply-To: <3bbf2fe10811230502t3cc52809i6ac91082f780b730@mail.gmail.com> References: <3bbf2fe10811230502t3cc52809i6ac91082f780b730@mail.gmail.com>
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I know I am going to really show my FreeBSD ignorance here, but this is a patch of FreeBSD 8.0 Current isn't it ? Thanks Ray Kinsella On Sun, Nov 23, 2008 at 1:02 PM, Attilio Rao <attilio@freebsd.org> wrote: > pmcannotate is a tool that prints out sources of a tool (in C or > assembly) with inlined profiling informations retrieved by a prior > pmcstat analysis. > If compared with things like callgraph generation, it prints out > profiling on a per-instance basis and this can be useful to find, for > example, badly handled caches, too high latency instructions, etc. > > The tool usage is pretty simple: > pmcannotate [-a] [-h] [-k path] [-l level] samples.out binaryobj > > where samples.out is a pmcstat raw output and binaryobj is the binary > object that has been profiled and is accessible for (ELF) symbols > retrieving. > The options are better described in manpages but briefly: > - a: performs analysis on the assembly rather than the C source > - h: usage and informations > - k: specify a path for the kernel in order to locate correct objects for > it > - l: specify a lower boundary (in total percentage time) after which > functions will be displayed nomore. > > A typical usage of pmcannotate can be some way of kernel annotation. > For example, you can follow the steps below: > 1) Generate a pmc raw output of system samples: > # pmcstat -S ipm-unhalted-core-cycles -O samples.out > 2) Copy the samples in the kernel building dir and cd there > # cp samples.out /usr/src/sys/i386/compile/GENERIC/ ; cd > /usr/src/sys/i386/compile/GENERIC/ > 3) Run pmcannotate > # pmcannotate -k . samples.out kernel.debug > kernel.ann > > In the example above please note that kernel.debug has to be used in > order to produce a C annotated source. This happens because in order > to get the binary sources we rely on the "objdump -S" command which > wants binary compiled with debugging options. > If not debugging options are present assembly analynsis is still > possible, but no C-backed one will be available. > objdump is not the only one tool on which pmcannotare rely. Infact, in > order to have it working, pmcstat needs to be present too because we > need to retrieve, from the pmcstat raw output, informations about the > sampled PCs (in particular the name of the function they live within, > its start and ending addresses). As long as currently pmcstat doesn't > return those informations, a new option has been added to the tool > (-m) which can extract (from a raw pmcstat output) all pc sampled, > name of the functions and symbol bundaries they live within. > > Also please note that pmcannotate suffers of 2 limitations. > Firstly, relying on objdump to dump the C source, with heavy > optimization levels and lots of inlines the code gets difficult to > read. Secondly, in particular on x86 but I guess it is not the only > one case, the sample is always attributed to the instruction directly > following the one that was interrupted. So in a C source view some > samples may be attributed to the line below the one you're interested > in. It's also important to keep in mind that if a line is a jump > target or the start of a function the sample really belongs elsewhere. > > The patch can be found here: > http://www.freebsd.org/~attilio/pmcannotate.diff/<http://www.freebsd.org/%7Eattilio/pmcannotate.diff/>; > > where pmcannotate/ dir contains the code and needs to go under > /usr/src/usr.sbin/ and the patch has diffs against pmcstat and > Makefile. > > This work has been developed on the behalf of Nokia with important > feedbacks and directions from Jeff Roberson. > > Testing and feedbacks (before it hits the tree) are welcome. > > Thanks, > Attilio > > > -- > Peace can only be achieved by understanding - A. Einstein > _______________________________________________ > freebsd-performance@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-performance > To unsubscribe, send any mail to " > freebsd-performance-unsubscribe@freebsd.org" >
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