Re: [PATCH] perf record: mmap output file - v2
From: David Ahern
Date: Tue Oct 15 2013 - 21:58:43 EST
On 10/15/13 7:52 PM, Namhyung Kim wrote:
Aha, okay. So it mostly matters to syscall tracing, right? For a
normal record session, it seems that the effect is not that large:
Yes, that's in the description "When recording raw_syscalls for the
entire system"
There is a small benefit to all record sessions -- mmap+memcpy has less
overhead than write(). I still need to look at Ingo's suggestion to use
non-temporal stores which might reduce the overhead of the memcpy.
Try a workload that generates a HUGE data file -- say a full kernel
build (e.g., perf record -g -- make O=/tmp/kbuild -j 16). You should see
a much larger benefit from the mmap route. Be sure to use your callchain
enhancements to look at that 1+G file. ;-)
David
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/