[PATCH]x86: update REP_STOSB_THRESHOLD's default value from 2k to 1M

[Siddhesh Poyarekar]

On 5/23/20 9:40 AM, liqingqing wrote:
> this commitid 830566307f038387ca0af3fd327706a8d1a2f595 optimize implementation of function memset,
> and set macro REP_STOSB_THRESHOLD's default value to 2KB, when the input value is less than 2KB, the data flow is the same, and when the input value is large than 2KB,
> this api will use STOB to instead of  MOVQ
> 
> but when I test this API on x86_64 platform
> and found that this default value is not appropriate for some input length. here it's the enviornment and result

This patch is not needed anymore since the threshold has been made a 
tunable: glibc.cpu.x86_rep_movsb_threshold.

Siddhesh