Re: [tip:perfcounters/core] perf_counter: record time running andtime enabled for each counter
From: Corey Ashford
Date: Wed Mar 25 2009 - 17:35:23 EST
Paul Mackerras wrote:
Commit-ID: 03ced439c94d692363307eeb3abe0bbfa2d08a01
Gitweb: http://git.kernel.org/tip/03ced439c94d692363307eeb3abe0bbfa2d08a01
Author: Paul Mackerras <paulus@xxxxxxxxx>
AuthorDate: Wed, 25 Mar 2009 22:46:58 +1100
Committer: Ingo Molnar <mingo@xxxxxxx>
CommitDate: Wed, 25 Mar 2009 13:24:00 +0100
perf_counter: record time running and time enabled for each counter
[snip]
These values can be supplied to userspace on a read from the counter.
Userspace requests that they be supplied after the counter value by
setting the PERF_FORMAT_TOTAL_TIME_ENABLED and/or
PERF_FORMAT_TOTAL_TIME_RUNNING bits in the hw_event.read_format field
when creating the counter. (There is no way to change the read format
after the counter is created, though it would be possible to add some
way to do that.)
This change looks good to me, except:
How do I know which value comes first after the counter value if I have
both PERF_FORMAT_TOTAL_TIME_ENABLED and PERF_FORMAT_TOTAL_TIME_RUNNING
set? Are they in the order of their enum values? The order should be
described somewhere. Is there anything to keep a kernel code change
from inadvertantly reversing the position of two values at some point in
the future?
Regards,
- Corey
Corey Ashford
Software Engineer
IBM Linux Technology Center, Linux Toolchain
Beaverton, OR
503-578-3507
cjashfor@xxxxxxxxxx
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