linux-kernel - Re: [PATCH v4 3/3] mm/free_pcppages_bulk: prefetch buddy while not holding lock

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Date:   Fri, 2 Mar 2018 10:00:24 -0800
From:   Dave Hansen <dave.hansen@...el.com>
To:     Vlastimil Babka <vbabka@...e.cz>, Michal Hocko <mhocko@...nel.org>,
        Aaron Lu <aaron.lu@...el.com>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        Huang Ying <ying.huang@...el.com>,
        Kemi Wang <kemi.wang@...el.com>,
        Tim Chen <tim.c.chen@...ux.intel.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Matthew Wilcox <willy@...radead.org>,
        David Rientjes <rientjes@...gle.com>
Subject: Re: [PATCH v4 3/3] mm/free_pcppages_bulk: prefetch buddy while not
 holding lock

On 03/02/2018 09:55 AM, Vlastimil Babka wrote:
> It's even stranger to me. Struct page is 64 bytes these days, exactly a
> a cache line. Unless that changed, Intel CPUs prefetched a "buddy" cache
> line (that forms an aligned 128 bytes block with the one we touch).

I believe that was a behavior that was specific to the Pentium 4
"Netburst" era.  I don't think the 128-byte line behavior exists on
modern Intel cpus.