Subject: Re: [linux-audio-dev] Memory Debugger
From: Paul Davis (pbd_AT_op.net)
Date: Thu May 23 2002 - 17:24:22 EEST
>> i find the x86 hardware watchpoint way, way, way too slow to be
>> useful, most of the time. on some hard problems in non-RT code, its
>> the only way. in RT code, its worse than useless :(
>>
>> --p
>>
>
>Really? I remember reading an Intel Pentium manual a while ago and
>drooling over the debug registers. I thought code execution was only
>slowed down when one wanted to trap the problem at the exact
>instruction. If it was not in this mode then the CPU exception would
>occur possibly several instructions after the fact. Anyways. Perhaps GDB
>only uses the first mode mentioned. Cheers.
yes, but a hardware memory watch point is totally different than an
instruction breakpoint. in the latter, you typically replace the
relevant instruction with a special one that will signal the hardware,
then the OS, then the debugger (via ptrace(2)). for a watch point,
there is no way to know what instruction will write to what memory, so
it can't be handled so efficiently.
--p
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