linux-kernel - Re: [RFC PATCH 2/2] mm/sparse: add last_section_nr in sparse

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:   Sat, 11 Feb 2017 11:24:00 +0900
From:   Tejun Heo <tj@...nel.org>
To:     Wei Yang <richard.weiyang@...il.com>
Cc:     akpm@...ux-foundation.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH 2/2] mm/sparse: add last_section_nr in sparse_init()
 to reduce some iteration cycle

Hello,

On Sat, Feb 11, 2017 at 10:18:29AM +0800, Wei Yang wrote:
> During the sparse_init(), it iterate on each possible section. On x86_64,
> it would always be (2^19) even there is not much memory. For example, on a
> typical 4G machine, it has only (2^5) to (2^6) present sections. This
> benefits more on a system with smaller memory.
> 
> This patch calculates the last section number from the highest pfn and use
> this as the boundary of iteration.

* How much does this actually matter?  Can you measure the impact?

* Do we really need to add full reverse iterator to just get the
  highest section number?

Thanks.

-- 
tejun