Messages in this thread | | | From | Vince Weaver <> | Date | Fri, 11 Aug 2017 12:51:12 -0400 (EDT) | Subject | Re: perf: multiple mmap of fd behavior on x86/ARM |
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On Fri, 11 Aug 2017, Mark Rutland wrote:
> IIRC, patches were sent back in 2014, but as I mentioned above, those > were far from suitable for upstream, even ignoring cases like > big.LITTLE. Said patches were never reworked and reposted.
Here's the commit message in the perf_event_tests tree, having trouble finding the original e-mail that went with it.
commit 2cc2e21e349243889ba59408527cc1a97dd0dc44 Author: Yogesh Tillu <yogesh.tillu@linaro.org> Date: Tue Mar 1 14:18:22 2016 +0530
Add support for RDPMC test with mmap way
This test adds support for reading perf hw counter from userspace. Method (2) rdpmc_comparision_mmap: Test read perf hw counter in userspace using open/mmap syscall. It requires kernel with perf mmap patchset and echo 1 > /sys/bus/platform/drivers/armv8-pmu/rdpmc Above Method Tested On:(X86/ARM) It is tested with perf mmap patchset on kernel v4.5.0-rc5+ With above Tests, we can benchmark access of perf hw counters in userspace with syscall vs perf_event_mmap_page way. Signed-off-by: Yogesh Tillu <yogesh.tillu@linaro.org>
> Just to check, how does x86 behave on each of those kernel releases? > > Many things have changed since v4.4.
I'm fairly sure this test (well, the equivelent code in tests/record_sample/record_mmap that I based the test on) has been passing on all of my x86 test machines since ~3.10 or so, or else I would noticed.
If I can get a custom kernel to boot on one of my machines I can start digging in and see if I can find where the EINVAL comes from.
This isn't some key thing that needs to be fixed, I was just curious about the behavior difference between x86 and ARM. There are a few other minor x86/ARM diferences, especially realting to perf_event_open() error returns, that I had to special case in a few of my tests.
Vince
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