[PATCH] net/pcap: reduce time for stopping device

[Stephen Hemminger]

On Mon, 29 Aug 2022 11:50:29 +0000
"Zhou, YidingX" <yidingx.zhou at intel.com> wrote:

> I draw a diagram to describe it more clearly
> 
>  fwrite                             fclose/fflush                                                   fclose/fdatasync
> --------->| libc buffer  |----------------> |    disk cache in RAM          |---------------------> |disk|  
>               | 4096 Bytes |                         | size is determined by OS |                                |       |
> 
> When the libc buffer is full, the system will automatically sync it to the disk cache.
> It is easily full as it's only 4096 B size. so there is no need to call 'fflush()' every time.
> The real time consuming action is syncing the disk cache to disk.
> Because the disk cache is very large, it will take a long time to sync all at one time during 'fclose()',
> so need to call 'fdatasync()' periodically to amortize the time.

If you want to speed up this, then get rid of stdio and use a faster
API like io_uring. What you tried can help but using a better API
would make bigger gains.