Re: [PATCH v3 net-next 16/16] tcp_bbr: add BBR congestion control

It generates some slightly smaller code.
        if (bbr->lt_rtt_cnt < bbr_lt_intvl_min_rtts)
- 3e7:  0f b6 c0                movzbl %al,%eax
- 3ea:  83 f8 03                cmp    $0x3,%eax
- 3ed:  0f 86 d4 00 00 00       jbe    4c7 <bbr_lt_bw_sampling.isra.6+0x157>
+ 3e7:  3c 03                   cmp    $0x3,%al
+ 3e9:  0f 86 d1 00 00 00       jbe    4c0 <bbr_lt_bw_sampling.isra.6+0x150>

And different code for abs
                /* Is new bw close to the lt_bw from the previous interval? */
                diff = abs(bw - bbr->lt_bw);
- 47a:  44 89 e2                mov    %r12d,%edx
- 47d:  29 c2                   sub    %eax,%edx
- 47f:  89 d1                   mov    %edx,%ecx
- 481:  89 d3                   mov    %edx,%ebx
+ 475:  44 89 e3                mov    %r12d,%ebx
+ 478:  29 c3                   sub    %eax,%ebx
+ 47a:  89 da                   mov    %ebx,%edx
+ 47c:  c1 fa 1f                sar    $0x1f,%edx
+ 47f:  31 d3                   xor    %edx,%ebx
+ 481:  29 d3                   sub    %edx,%ebx

The biggest change is getting rid of the always true conditional.

...

Overall, it really makes little difference. Actual file sizes come out the same.
The idea is more to document what is variable
and what is immutable in the algorithm.

SGTM, thanks Stephen !