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Re: Memory Transactions per Second.

Cross-posted to 5 groups.

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On 6/11/2011 10:57 PM, Skybuck Flying wrote:
> Hello,
>
> I would like to know how many "random locations" in a memory system can
> be read or written to per second.
>
> This could also be called "memory transactions per second".
>
> The devil is in the details, for example:
>
> A spec might say: 32.000.000.000 bytes/sec of bandwidth.

This is a really important metric.  But, unfortunately, it is often hard 
to tell from published specs or benchmarks.

(By the way, a networking guy a few years ago proposed that this become 
a standard metric, which he called (random) address bandwidth - since 
each transaction would have a random address.)

As Mitch says, the only really good way to do this is to run your own 
benchmark.

Certain supercomputer benchmarks have aspects of this..  For example, 
GUPS is related - although it tends to do read-modify-writes.

It is usually quite hard, if not impossible, to determine this from 
published specs of a system.  As you have seen, memory bandwidth is 
usually measured on sequential access patterns, and is barely related to 
random address bandwidth.

You can make a start if you can determine the timing for a worst case 
DRAM access, that requires closing an open page, precharging, accessing, 
etc.

But this does not tell you about the internals inside the processor. 
Cache and queing overheads, etc.

In particular, you need to say whether you want dependent addresses, or 
independent.

If independent, you will eventually be measuring the amount  of 
buffering in the memory system. And the number of memory channnels, DIM 
ranks, etc. - basically, the amount to which you can overlap transactions.

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Memory Transactions per Second. "Skybuck Flying" <Windows7IsOK@DreamPC2006.com> - 2011-06-12 07:57 +0200
  Re: Memory Transactions per Second. MitchAlsup <MitchAlsup@aol.com> - 2011-06-12 08:59 -0700
    Re: Memory Transactions per Second. "Skybuck Flying" <Windows7IsOK@DreamPC2006.com> - 2011-06-12 23:42 +0200
      Re: Memory Transactions per Second. Robert Redelmeier <redelm@ev1.net.invalid> - 2011-06-13 02:49 +0000
        Re: Memory Transactions per Second. "Skybuck Flying" <Windows7IsOK@DreamPC2006.com> - 2011-06-13 16:50 +0200
          Re: Memory Transactions per Second. Robert Redelmeier <redelm@ev1.net.invalid> - 2011-06-15 02:49 +0000
            Re: Memory Transactions per Second. "Skybuck Flying" <Windows7IsOK@DreamPC2006.com> - 2011-06-15 06:55 +0200
  Re: Memory Transactions per Second. "Andy \"Krazy\" Glew" <andy@SPAM.comp-arch.net> - 2011-06-12 12:51 -0700
    Re: Memory Transactions per Second. MitchAlsup <MitchAlsup@aol.com> - 2011-06-12 14:40 -0700
    Re: Memory Transactions per Second. Jason Riedy <jason@lovesgoodfood.com> - 2011-06-13 09:33 -0400
  Re: Memory Transactions per Second. mr computer <microbrainz@gmail.com> - 2011-06-12 16:06 -0700
    Re: Memory Transactions per Second. "Skybuck Flying" <Windows7IsOK@DreamPC2006.com> - 2011-06-13 16:29 +0200
      Re: Memory Transactions per Second. mr computer <microbrainz@gmail.com> - 2011-06-13 07:54 -0700
        Re: Memory Transactions per Second. "Skybuck Flying" <Windows7IsOK@DreamPC2006.com> - 2011-06-13 17:08 +0200
          Re: Memory Transactions per Second. MitchAlsup <MitchAlsup@aol.com> - 2011-06-13 11:50 -0700
            Re: Memory Transactions per Second. "Skybuck Flying" <Windows7IsOK@DreamPC2006.com> - 2011-06-14 04:07 +0200

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