Re: [Question] How does perf still record the stack of a specified pid even when that process is interrupted and CPU is scheduled to other process

From: Yunlong Song
Date: Fri Apr 24 2015 - 09:56:27 EST

On 2015/4/24 21:49, David Ahern wrote:
> On 4/24/15 7:31 AM, Yunlong Song wrote:
>> [Profiling Problem]
>> Although perf can record the events (with call stack) of a specified pid, e.g. using
>> "perf record -g iozone -s 262144 -r 64 -i 0 -i 2". But we find iozone is interrupted
> That command tells perf to *only* collect data for iozone. This command:
> perf record -g -a -- iozone ....
> tells perf to collect samples system wide as long as the iozone process is alive.

But we only want the records of iozone rather than the overall system, since other process
will interfere the targeted I/O stack of the specific 1% case, and we cannot figure out the
"clean" specific stack which takes up 60% time.

Yunlong Song

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