Re: Suggestion to optimize posix_getxattr call

[Amar Tumballi <atumball@xxxxxxxxxx>]

On Mon, May 15, 2017 at 2:56 PM, Mohit Agrawal <moagrawa@xxxxxxxxxx> wrote:

Hi,

  I was just checking of posix_getxattr code to debug of my one problem.I have found scope of improvement in 

  this function to execute system call in better way.As of now function(posix_getxattr) is calling system 

  calls (sys_lgetxattr) two times to get the value of xattr or in case of list of xattr it calls multiple times

  

 1) In first time it get the buffer size required to store the value.

     call "size = sys_lgetxattr (real_path, key, NULL, 0);"

 2) In second time it calls the sys_lgetxattr with buffer after allocate the buffer size

     sys_lgetxattr (real_path, key, value, size);

  In the same way function is calling for listxattr also.I think we can optimise it as like below

  declare buffer buf[8192](size can be double to this also)

  1) Call size = sys_lgetxattr (real_path,key,buf,8192)

  2) if size == -1 and errono == ERANGE then we need to call systemcalls in old way like above otherwise

     we don't need to do anything.

 

  In the case of failure we need to call systemcall 3 times while buffer is more than our declared buffer

  size otherwise in most of the cases we need to call it only once.

+1.

Please add a counter for the number of times the failure happens with ERANGE, and see if we can log offender keys. Helps to adjust the size later.

-Amar

    Please share your input on this, appreciate your input.

Regards

Mohit Agrawal

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--

Amar Tumballi (amarts)

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