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Date: Wed, 12 Feb 2020 09:26:08 -0800
From: Gleb Smirnoff <glebius@freebsd.org>
To: Mateusz Guzik <mjg@freebsd.org>
Cc: src-committers@freebsd.org, svn-src-all@freebsd.org,
 svn-src-head@freebsd.org
Subject: Re: svn commit: r357805 - head/sys/amd64/include
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On Wed, Feb 12, 2020 at 11:12:14AM +0000, Mateusz Guzik wrote:
M> Author: mjg
M> Date: Wed Feb 12 11:12:13 2020
M> New Revision: 357805
M> URL: https://svnweb.freebsd.org/changeset/base/357805
M> 
M> Log:
M>   amd64: store per-cpu allocations subtracted by __pcpu
M>   
M>   This eliminates a runtime subtraction from counter_u64_add.
M>   
M>   before:
M>   mov    0x4f00ed(%rip),%rax        # 0xffffffff80c01788 <numfullpathfail4>
M>   sub    0x808ff6(%rip),%rax        # 0xffffffff80f1a698 <__pcpu>
M>   addq   $0x1,%gs:(%rax)
M>   
M>   after:
M>   mov    0x4f02fd(%rip),%rax        # 0xffffffff80c01788 <numfullpathfail4>
M>   addq   $0x1,%gs:(%rax)
M>   
M>   Reviewed by:	jeff
M>   Differential Revision:	https://reviews.freebsd.org/D23570

Neat optimization! Thanks. Why didn't we do it back when created counter?

-- 
Gleb Smirnoff