How to measure the RAM read/write performance

[buyitian]

________________________________
> From: coolsandyforyou at gmail.com 
> Date: Tue, 26 Feb 2013 17:01:54 +0530 
> Subject: How to measure the RAM read/write performance 
> To: kernelnewbies at kernelnewbies.org 
> CC: dhylands at gmail.com 
> 
> Hi All 
> In performance benchmark tools, When we profile read/write timings 
> mostly, those read/writes are done to cache only. 
> 
> I want to measure my DDR(RAM chip) performance. 
> So i want to make sure, every read/write should happen to DDR RAM chip only. 
> 
> How can i achieve this...Any ideas/suggestions...? 

try to reserve a large region from bootloader(L4 in Qualcomm platform), let's say it is 10MB continuous physical memory.
in kernel, map this region to an continuous virtual region, note that the pgprot should be uncachable since you want to test without cache.
once you configed like this, you can read/write to this vitual region without data cache invovled.

> 
> -- 
> With regards, 
> Sandeep Kumar Anantapalli, 
> 
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