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Re: [PATCH 1/2] [GDBserver] Fix compiling conditional expressions accessing registers
- From: Yao Qi <qiyaoltc at gmail dot com>
- To: Pedro Alves <palves at redhat dot com>
- Cc: Ulrich Weigand <uweigand at de dot ibm dot com>, Yao Qi <qiyaoltc at gmail dot com>, Pierre Langlois <pierre dot langlois at arm dot com>, gdb-patches at sourceware dot org, cole945 at gmail dot com
- Date: Wed, 16 Sep 2015 16:03:18 +0100
- Subject: Re: [PATCH 1/2] [GDBserver] Fix compiling conditional expressions accessing registers
- Authentication-results: sourceware.org; auth=none
- References: <20150916115014 dot 0A5EA1DA8 at oc7340732750 dot ibm dot com> <55F97479 dot 9070807 at redhat dot com>
Pedro Alves <palves@redhat.com> writes:
>> Not sure whether this is a real performance concern for actual use
>> cases though. I don't have any actual measurements ...
>
> Yes, I was just now reading this, and was going to say the same.
>
> E.g., the original fast tracepoints code was tuned to avoid as much
> work as possible in the condition-fails scenario, when the condition
> only accesses a global. That is, e.g., "trace foo if debug_knob == 1".
> I no longer have the numbers captured at the time though.
I run tspeed.exp, and it shows this patch slows down fast tracepoint
from 29ns to 144ns, so we need to commit Wei-chang's patch
<https://sourceware.org/ml/gdb-patches/2015-06/msg00587.html> instead.
--
Yao (éå)