Messages in this thread | | | Date | Mon, 19 Dec 2011 11:54:29 +0100 | From | Ingo Molnar <> | Subject | Re: [RFC 4/5] x86, perf: implements lwp-perf-integration (rc1) |
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* Robert Richter <robert.richter@amd.com> wrote:
> On 19.12.11 00:43:10, Ingo Molnar wrote: > > > So the question becomes, how well is it integrated: can perf > > 'record -a + perf report', or 'perf top' use LWP, to do > > system-wide precise [user-space] profiling and such? > > There is only self-monitoring of a process possible, no kernel > and system-wide profiling. This is because we can not allocate > memory regions in the kernel for a thread other than the > current. This would require a complete rework of mm code.
Hm, i don't think a rework is needed: check the vmalloc_to_page() code in kernel/events/ring_buffer.c. Right now CONFIG_PERF_USE_VMALLOC is an ARM, MIPS, SH and Sparc specific feature, on x86 it turns on if CONFIG_DEBUG_PERF_USE_VMALLOC=y.
That should be good enough for prototyping the kernel/user shared buffering approach.
Thanks,
Ingo
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