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

[Vlastimil Babka]

On 03/02/2018 07:00 PM, Dave Hansen wrote:
> 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.

I remember it on Core 2 something (Nehalem IIRC). And this page suggests
up to Broadwell, and it can be disabled. And it's an L2 prefetcher indeed.
https://software.intel.com/en-us/articles/disclosure-of-hw-prefetcher-control-on-some-intel-processors