linux-kernel - Re: [RFC PATCH 03/15] mm: memcontrol: remove the pgdata parameter of mem_cgroup_page

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:   Fri, 2 Apr 2021 11:22:11 -0400
From:   Johannes Weiner <hannes@...xchg.org>
To:     Muchun Song <songmuchun@...edance.com>
Cc:     guro@...com, mhocko@...nel.org, akpm@...ux-foundation.org,
        shakeelb@...gle.com, vdavydov.dev@...il.com,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        duanxiongchun@...edance.com
Subject: Re: [RFC PATCH 03/15] mm: memcontrol: remove the pgdata parameter of
 mem_cgroup_page_lruvec

On Tue, Mar 30, 2021 at 06:15:19PM +0800, Muchun Song wrote:
> All the callers of mem_cgroup_page_lruvec() just pass page_pgdat(page)
> as the 2nd parameter to it (except isolate_migratepages_block()). But
> for isolate_migratepages_block(), the page_pgdat(page) is also equal
> to the local variable of @pgdat. So mem_cgroup_page_lruvec() do not
> need the pgdat parameter. Just remove it to simplify the code.
> 
> Signed-off-by: Muchun Song <songmuchun@...edance.com>

There is a minor benefit in not doing the page_pgdat() lookup twice.
But I think it only really matters on 32-bit NUMA, where we have more
than one node but not enough space in page->flags to store the nid,
and so page_to_nid() is out-of-line and needs to go through section.

Those setups aren't really around anymore, and certainly don't justify
the hassle (and potential bugs) of the awkward interface.

Acked-by: Johannes Weiner <hannes@...xchg.org>