Messages in this thread | | | Date | Fri, 30 Oct 2009 03:54:01 +0530 | From | "K.Prasad" <> | Subject | Re: [RFC Patch 0/4] Enhance perf-events to profile memory accesses using hw-breakpoints - ver II |
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On Thu, Oct 29, 2009 at 09:19:17AM +0100, Ingo Molnar wrote: > > * K.Prasad <prasad@linux.vnet.ibm.com> wrote: > [snipped] > > > > # > > # > > # perf record -v -i -e breakpoint-readwrite:jiffies top > > > > [Ran 'top' for about 10 seconds] > > btw., you probably want to add the -a/--all option as well when you test > via top, to do system-wide profiling. With this command you profile top > itself (and its child tasks). >
Okay. Attached output to that effect in ver III of my patchset sent here: http://lkml.org/lkml/2009/10/29/300
> > > > # perf report -i perf.data > > # Samples: 2022950155 > > # > > # Overhead Command Shared Object Symbol > > # ........ ....... ............. ...... > > # > > 99.99% top [kernel] [k] scheduler_tick > > 0.01% perf [kernel] [k] scheduler_tick > > 0.00% top [kernel] [k] set_track > > 0.00% top [kernel] [k] run_timer_softirq > > 0.00% perf [kernel] [k] set_track > > 0.00% top [kernel] [k] __call_rcu > > 0.00% top [kernel] [k] calc_global_load > > 0.00% top [kernel] [k] do_timer > > 0.00% top [kernel] [k] __rcu_process_callbacks > > # > > # (For a higher level overview, try: perf report --sort comm,dso) > > # > > That output looks pretty awesome! This way we can map out how frequently > global variables are used in the kernel - in stock distro kernels too. > Previously we could only measure it indirectly (by looking at > high-overhead functions and assembly level annotations), or by running > very costly instrumentation like Valgrind. > > I like it how you extended --event with the breakpoint-readwrite:jiffies > method as well. > > A few additional shortcuts/aliases would be nice, such as: > > perf record -v -i -e readwrite:jiffies top > > as breakpoint-readwrite is pretty log users arent really interested in > the mechanism (hardware-breakpoints), they are more interested that it's > memory read-write profiling done at a given address. > > Maybe even 'rw' would be a useful alias as well. There are alias tables > for events which you can use for this. You can define them via: > > { CHBP(WRITE), "memory-write", "write", "w" }, > { CHBP(RW), "memory-readwrite", "readwrite", "rw" }, >
I've added "memory-write" and "w" as the aliases (similarly "memory-readwrite" and "rw" as shown under). "read" and "write" are used as hw_cache_op[] aliases; moreover defining more than one alias would require a separate structure (as done by hw_cache[] and hw_cache_op[] and further changes in print_events()), and hence the single alias. I'm open to any further suggestions on the renaming front.
+ { CHBP(WRITE), "memory-write", "w" }, + { CHBP(RW), "memory-readwrite", "rw" },
> Anyway, this looks very good already - Frederic, if you like these > patches too feel free to send it to me in your next hw-breakpoints pull > request. > > Thanks, > > Ingo
I'm glad that you found value in the patchset and hope that this would entail the feature's journey further into the mainline. Frederic's previous mail suggests that I owe him more reasoning about the patches' approach, before being sent out for a git pull!
Thanks, K.Prasad
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