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Re: [PATCH v4 2/3] Support for perf to probe into SDT markers:
- From: Hemant Kumar <hkshaw at linux dot vnet dot ibm dot com>
- To: Pekka Enberg <penberg at iki dot fi>
- Cc: David Ahern <dsahern at gmail dot com>, Srikar Dronamraju <srikar at linux dot vnet dot ibm dot com>, LKML <linux-kernel at vger dot kernel dot org>, Peter Zijlstra <peterz at infradead dot org>, Oleg Nesterov <oleg at redhat dot com>, "hegdevasant at linux dot vnet dot ibm dot com" <hegdevasant at linux dot vnet dot ibm dot com>, Ingo Molnar <mingo at redhat dot com>, "anton at redhat dot com" <anton at redhat dot com>, "systemtap at sourceware dot org" <systemtap at sourceware dot org>, Namhyung Kim <namhyung at kernel dot org>, Masami Hiramatsu <masami dot hiramatsu dot pt at hitachi dot com>, "aravinda at linux dot vnet dot ibm dot com" <aravinda at linux dot vnet dot ibm dot com>
- Date: Wed, 30 Oct 2013 01:11:26 +0530
- Subject: Re: [PATCH v4 2/3] Support for perf to probe into SDT markers:
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On 10/29/2013 07:35 PM, Pekka Enberg wrote:
On 10/29/2013 11:55 AM, Hemant Kumar wrote:
1. Where this cache should be? Keeping it in tracing directory inside
the debugfs
directory should seem more feasible. And, shall this cache be shareable?
You can't share all of the cache because otherwise you'll expose
details on binaries that not everyone has access to.
Correct, that was one of the reason to be worried. And since, to a
normal user debugfs is not allowed to be entered, then we can keep that
inside debugfs/tracing subdirectory.
It might make sense to split the cache into two parts: system markers
and user markers and share the former.
Ok...
2. perf record is a performance intensive process, can we allow the
delay due to
this searching process here?
I think scanning is OK if the user specified a SDT markers but not
otherwise.
Perhaps you can use a bloom filter to quickly check if the user passed
a SDT marker or not.
True, bloom filters may help in this case with a quick check.
--
Thanks
Hemant Kumar