linux-kernel - Re: [PATCH 1/6] mm/page_alloc: Delete vm.percpu_pagelist

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]

Message-ID: <bd19a014-f5bb-eb75-e44c-51d14cd62868@intel.com>
Date:   Fri, 21 May 2021 14:04:25 -0700
From:   Dave Hansen <dave.hansen@...el.com>
To:     Mel Gorman <mgorman@...hsingularity.net>,
        Linux-MM <linux-mm@...ck.org>
Cc:     Dave Hansen <dave.hansen@...ux.intel.com>,
        Matthew Wilcox <willy@...radead.org>,
        Vlastimil Babka <vbabka@...e.cz>,
        Michal Hocko <mhocko@...nel.org>,
        Nicholas Piggin <npiggin@...il.com>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/6] mm/page_alloc: Delete vm.percpu_pagelist_fraction

On 5/21/21 3:28 AM, Mel Gorman wrote:
> The vm.percpu_pagelist_fraction is used to increase the batch and high
> limits for the per-cpu page allocator (PCP). The intent behind the sysctl
> is to reduce zone lock acquisition when allocating/freeing pages but it has
> a problem. While it can decrease contention, it can also increase latency
> on the allocation side due to unreasonably large batch sizes. This leads
> to games where an administrator adjusts percpu_pagelist_fraction on the
> fly to work around contention and allocation latency problems.
> 
> This series aims to alleviate the problems with zone lock contention while
> avoiding the allocation-side latency problems. For the purposes of review,
> it's easier to remove this sysctl now and reintroduce a similar sysctl
> later in the series that deals only with pcp->high.
> 
> Signed-off-by: Mel Gorman <mgorman@...hsingularity.net>

I despise working with percpu_pagelist_fraction.  I usually just end up
poking random numbers into it and then checking what the fallout looks
like in /proc/zoneinfo is.

Good riddance.

Acked-by: Dave Hansen <dave.hansen@...ux.intel.com>