>1. use early_param to get the physical start address and size of test_region, or you can just ignore this step and hard code to 510M and 2M for test purpose only.
>2. use ioremap_nocache() to map this region to a virtual region. note that this funtion may fail if you are asking a very large vitual memroy region. Sounds good, i am gonna try this and let you know.. :) On Wed, Feb 27, 2013 at 8:19 PM, buyitian <bu...@live.cn> wrote: > ---------------------------------------- > > From: bu...@live.cn > > To: coolsandyfor...@gmail.com; kernelnewbies@kernelnewbies.org > > Subject: RE: How to measure the RAM read/write performance > > Date: Wed, 27 Feb 2013 22:33:15 +0800 > > CC: dhyla...@gmail.com > > > > ________________________________ > > > From: coolsandyfor...@gmail.com > > > Date: Tue, 26 Feb 2013 17:01:54 +0530 > > > Subject: How to measure the RAM read/write performance > > > To: kernelnewbies@kernelnewbies.org > > > CC: dhyla...@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. > > sorry, to be accurate, reserve physical memory is done by kernel cmdline, > this cmdline parameter can be passed from L4 to kernel, or configed by > kernel itself. > the cmdline will be like below: > mem=510M@0 test_region=2M@510M > > above example tells kernel you have totally 512MB physical memory, but > kernel will only use the first 510MB, the latter 2MB memory is used by you. > how to map and use this region depends on you. > > > in kernel, map this region to an continuous virtual region, note that > the pgprot should be uncachable since you want to test without cache. > > 1. use early_param to get the physical start address and size of > test_region, or you can just ignore this step and hard code to 510M and 2M > for test purpose only. > > 2. use ioremap_nocache() to map this region to a virtual region. note that > this funtion may fail if you are asking a very large vitual memroy region. > > > once you configed like this, you can read/write to this vitual region > without data cache invovled. > > > > > > > > -- > > > With regards, > > > Sandeep Kumar Anantapalli, > > > > > > _______________________________________________ Kernelnewbies mailing > > > list Kernelnewbies@kernelnewbies.org > > > http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies > > _______________________________________________ > > Kernelnewbies mailing list > > Kernelnewbies@kernelnewbies.org > > http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies > > -- With regards, Sandeep Kumar Anantapalli,
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