how to trace tcp protocol stack ?

2013-03-03 Thread ishare 
hi:)

   Is there mothod to look up the call stack of tcp protocol solution?

thanks!

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Re: how to trace tcp protocol stack ?

2013-03-03 Thread richard -rw- weinberger 
On Sun, Mar 3, 2013 at 5:13 AM, ishare june.tune@gmail.com wrote:
 hi:)

Is there mothod to look up the call stack of tcp protocol solution?

You can use ftrace.

-- 
Thanks,
//richard

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Re: how to trace tcp protocol stack ?

2013-03-03 Thread Valdis . Kletnieks 
On Sun, 03 Mar 2013 12:13:51 +0800, ishare said:

Is there mothod to look up the call stack of tcp protocol solution?

ftrace and related functionality.

Note that there is a difference between look up the call stack
and trace the flow of execution.  Consider the following code:

int a ( print(a) } ;
int b { print(b) } ;
int c ( a(); b(); };
int d  { c(); b() };

If you print the call stack in a(), you'll get a c d.

If you trace the flow, you get d c a b b  (plus some returns scattered
in between.

The difference is subtle, but often important.  If you're trying to
figure out how it works, you probably want to trace the flow.  If you're
trying to figure out how the code *got* to function foobar(), you're
looking at a stack trace.

Also, being familiar with the RFCs that define TCP is helpful.  In
particular, the Linux TCP stack will make close to zero sense unless
you're familiar with the state machine defined in RFC793.


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Re: How to measure the RAM read/write performance

2013-03-03 Thread Arun KS 
Hi Sandeep,

On Sat, Mar 2, 2013 at 12:21 PM, sandeep kumar
coolsandyfor...@gmail.com wrote:
Another easy way to make memory(ie..pages) non cacheble is use the
below function,
dma_alloc_coherent(NULL, size, p, GFP_KERNEL);

 I did like what you said. With the timings,i can see it is reading directly
 from RAM. I have some doubts..
 -- What exactly happend here? Here read/write are done by CPU or DMA
 controller?

If you have used the virtual address returned by dma_alloc_coherent,
then obviously it is CPU who has done the read/write.

dma_alloc_coherent allocates memory, sets the page table attributes
for this memory as non cacheable.
When ever CPU access this memory, it generates virtual address, MMU
converts this to physical address using page tables.
Page tables has memory attributes which says that this memory is non-cachable.

Thanks,
Arun


 I am new to DMA kind of operations, i have one doubt in how to do DMA?
 Can you give me some example driver code, for this following case

 -- I want to do a DMA from a mem mapped I/O (lets say physical 0x4000)
 to RAM location @ 0x8000.
 How do you do this?

 Thanks
 Sandeep


 On Fri, Mar 1, 2013 at 10:45 AM, Arun KS getaru...@gmail.com wrote:

 On Thu, Feb 28, 2013 at 3:54 PM, sandeep kumar
 coolsandyfor...@gmail.com wrote:
 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.
  I did the following things,
 
  Thank you so much...It worked. With this i am able to measure RAM
  performance.

 Another easy way to make memory(ie..pages) non cacheble is use the
 below function,
 dma_alloc_coherent(NULL, size, p, GFP_KERNEL);

 This will set the page tables attributes for this page no-cachable.
 All reads  writes will always happen from main memory because MMU see
 the memory attribute for this page as non cacheble.

 Thanks,
 Arun
 
 
  On Thu, Feb 28, 2013 at 11:39 AM, sandeep kumar
  coolsandyfor...@gmail.com
  wrote:
 
  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.
  I did the following things,
  1) Reserved 3MB memory through ATAGS
  2) Wrote small driver to ioremap that memory in following way,
 
   void *tcpm_base = ioremap_nocache(0x03B0, SZ_3MB);
   27 if(tcpm_base!=NULL)
   28 {
   29 printk(Jiffies %x %ld\n\n\n\n, jiffies, jiffies);
   30 for(i=0;iSZ_4KB;i++)
   31 src = readl(tcpm_base+i);
   32 printk(Jiffies %x %ld\n\n\n\n, jiffies, jiffies);
   33 }
   34 else
   35 printk(unable to map 3MB\n);
 
  3) I am getting the following error,
 
  [1.876647] Unable to handle kernel paging request at virtual
  address
  ea82c000
  [1.880950] pgd = c0004000
  [1.883636] [ea82c000] *pgd=49818811, *pte=, *ppte=
  [1.889892] Internal error: Oops: 7 [#1] PREEMPT
  [1.894500] Modules linked in:
  [1.897521] CPU: 0Not tainted  (3.0.31-g1080f34-dirty #106)
  [1.903442] PC is at sand_misc_init+0x4c/0xac
  [1.907775] LR is at sand_misc_init+0x3c/0xac
  [1.912109] pc : [c0022ee0]lr : [c0022ed0]psr: 8013
  [1.912139] sp : e982bf98  ip :   fp : 
  [1.923553] r10:   r9 :   r8 : 
  [1.928771] r7 :   r6 : c00461b4  r5 : ea828000  r4 :
  
  [1.935272] r3 : 3fff  r2 : 3ffd  r1 : c07ea2cf  r0 :
  0063
  [1.941802] Flags: Nzcv  IRQs on  FIQs on  Mode SVC_32  ISA ARM
  Segment kernel
  [1.949096] Control: 10c57c7d  Table: 00404059  DAC: 0015
  [1.954803]
  [1.954833] PC: 0xc0022e60:
  [1.959075] 2e60  c09105f0 c0366554 c07ea27e c07ea296 e3a01000
  e92d4010
  e1a02001 eb0a9acd
  [1.967224] 2e80  e59f3008 e5830008 e3a1 e8bd8010 c0dd8380
  e92d4037
  e3a04000 e3a0063b
  [1.975402] 2ea0  e3a01901 e1a02004 e5cd4007 e5cd4006 eb00b9aa
  e2505000
  0a19 e59f3070
  [1.983551] 2ec0  e59f0070 e5931000 e5932000 eb18a072 e58d4000
  e3033fff
  ea07 e59d2000
  [1.991699] 2ee0  e7952002 f57ff04f e6ef2072 e5cd2007 e59d2000
  e2822001
  e58d2000 e59d2000
  [1.999877] 2f00  e1520003 daf4 e59f3024 e59f0024 e5931000
  e5932000
  e28dd00c e8bd4030
  [2.008026] 2f20  ea18a05d e59f0010 e28dd00c e8bd4030 ea18a059
  c08ea600
  c07ea2cf c07ea2e2
  [2.016174] 2f40  e59f3040 e3a01000 e92d4010 e59f0038 e5932000
  eb0a845a
  e59f3030 e350
  [2.024353]
  [2.024353] LR: 0xc0022e50:
  [2.028594]

How to get RFC documents?

2013-03-03 Thread ishare 

Is there nice  way to get RFC doc by email?


thanks!

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