[Gluster-devel] Suggestion to optimize posix_getxattr call

[Amar Tumballi]

On Mon, May 15, 2017 at 2:56 PM, Mohit Agrawal <moagrawa at redhat.com> 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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