Groups > comp.os.linux.development.system > #216

Re: How to estimate System Memory Bandwidth by sampling

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From	Rainer Weikusat <rweikusat@mssgmbh.com>
Newsgroups	comp.os.linux.development.system
Subject	Re: How to estimate System Memory Bandwidth by sampling
Date	Wed, 13 Jul 2011 13:12:07 +0100
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Tim Roberts <timr@probo.com> writes:
> Xiaofeng Ye <yexfeng@gmail.com> wrote:
>>
>>I need such a method to estimate Used System Memory Bandwidth.
>>================================================
>>Get total amount of memory R/W bytes at Time1 and Time2. Then use the
>>following formula to estimate Used System Memory Bandwidth.
>>    UsedSystemMemoryBandwidth = (BytesAtTime2 - BytesAtTime1) / (Time2
>>- Time1)
>>================================================
>>
>>But I have not found any system metrics by which I can get the total
>>amount of memory R/W bytes. BTW, I'm not going to use CPU's PMU
>>(performance monitoring unit).
>>
>>I need some advice how to get memory R/W bytes from a user mode
>>program or from a kernel module.  (Hook is OK too)
>
> That's impossible.  This is not a statistic that software can keep track
> of.

Why this? All which seems to be needed for that is access to an area
of physical memory configured as uncached and some hardware
timer that can be used to measure the time it takes to execute some
'block memory access loop'.

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Thread

How to estimate System Memory Bandwidth by sampling Xiaofeng Ye <yexfeng@gmail.com> - 2011-07-10 20:20 -0700
  Re: How to estimate System Memory Bandwidth by sampling Tim Roberts <timr@probo.com> - 2011-07-13 00:01 -0700
    Re: How to estimate System Memory Bandwidth by sampling Rainer Weikusat <rweikusat@mssgmbh.com> - 2011-07-13 13:12 +0100
      Re: How to estimate System Memory Bandwidth by sampling Tim Roberts <timr@probo.com> - 2011-07-14 22:18 -0700
        Re: How to estimate System Memory Bandwidth by sampling Rainer Weikusat <rweikusat@mssgmbh.com> - 2011-07-15 16:24 +0100

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