linux-kernel - Re: [PATCH] mm/vmscan: try to optimize branch procedures.

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Tue, 28 Nov 2017 09:03:39 +0100
From:   Michal Hocko <mhocko@...nel.org>
To:     Jiang Biao <jiang.biao2@....com.cn>
Cc:     akpm@...ux-foundation.org, hannes@...xchg.org,
        hillf.zj@...baba-inc.com, minchan@...nel.org, ying.huang@...el.com,
        mgorman@...hsingularity.net, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, zhong.weidong@....com.cn
Subject: Re: [PATCH] mm/vmscan: try to optimize branch procedures.

On Tue 28-11-17 09:49:45, Jiang Biao wrote:
> 1. Use unlikely to try to improve branch prediction. The
> *total_scan < 0* branch is unlikely to reach, so use unlikely.
> 
> 2. Optimize *next_deferred >= scanned* condition.
> *next_deferred >= scanned* condition could be optimized into
> *next_deferred > scanned*, because when *next_deferred == scanned*,
> next_deferred shoud be 0, which is covered by the else branch.
> 
> 3. Merge two branch blocks into one. The *next_deferred > 0* branch
> could be merged into *next_deferred > scanned* to simplify the code.

How have you measured benefit of this patch?

-- 
Michal Hocko
SUSE Labs