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From: Vlastimil Babka <vbabka@suse.cz>
To: Dave Hansen <dave.hansen@intel.com>,
	Michal Hocko <mhocko@kernel.org>, Aaron Lu <aaron.lu@intel.com>
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org,
	Andrew Morton <akpm@linux-foundation.org>,
	Huang Ying <ying.huang@intel.com>,
	Kemi Wang <kemi.wang@intel.com>,
	Tim Chen <tim.c.chen@linux.intel.com>,
	Andi Kleen <ak@linux.intel.com>,
	Mel Gorman <mgorman@techsingularity.net>,
	Matthew Wilcox <willy@infradead.org>,
	David Rientjes <rientjes@google.com>
Subject: Re: [PATCH v4 3/3] mm/free_pcppages_bulk: prefetch buddy while not holding lock
Date: Fri, 2 Mar 2018 19:08:00 +0100	[thread overview]
Message-ID: <787e53b9-20d3-a2df-44fc-ea8c31a6ced3@suse.cz> (raw)
In-Reply-To: <2433e857-fea7-9af4-d124-538ad17de454@intel.com>

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

WARNING: multiple messages have this Message-ID (diff)
From: Vlastimil Babka <vbabka@suse.cz>
To: Dave Hansen <dave.hansen@intel.com>,
	Michal Hocko <mhocko@kernel.org>, Aaron Lu <aaron.lu@intel.com>
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org,
	Andrew Morton <akpm@linux-foundation.org>,
	Huang Ying <ying.huang@intel.com>,
	Kemi Wang <kemi.wang@intel.com>,
	Tim Chen <tim.c.chen@linux.intel.com>,
	Andi Kleen <ak@linux.intel.com>,
	Mel Gorman <mgorman@techsingularity.net>,
	Matthew Wilcox <willy@infradead.org>,
	David Rientjes <rientjes@google.com>
Subject: Re: [PATCH v4 3/3] mm/free_pcppages_bulk: prefetch buddy while not holding lock
Date: Fri, 2 Mar 2018 19:08:00 +0100	[thread overview]
Message-ID: <787e53b9-20d3-a2df-44fc-ea8c31a6ced3@suse.cz> (raw)
In-Reply-To: <2433e857-fea7-9af4-d124-538ad17de454@intel.com>

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


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  reply	other threads:[~2018-03-02 18:09 UTC|newest]

Thread overview: 67+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-03-01  6:28 [PATCH v4 0/3] mm: improve zone->lock scalability Aaron Lu
2018-03-01  6:28 ` Aaron Lu
2018-03-01  6:28 ` [PATCH v4 1/3] mm/free_pcppages_bulk: update pcp->count inside Aaron Lu
2018-03-01  6:28   ` Aaron Lu
2018-03-01 12:11   ` David Rientjes
2018-03-01 12:11     ` David Rientjes
2018-03-01 13:45   ` Michal Hocko
2018-03-01 13:45     ` Michal Hocko
2018-03-12 13:22   ` Vlastimil Babka
2018-03-13  2:11     ` Aaron Lu
2018-03-01  6:28 ` [PATCH v4 2/3] mm/free_pcppages_bulk: do not hold lock when picking pages to free Aaron Lu
2018-03-01  6:28   ` Aaron Lu
2018-03-01 13:55   ` Michal Hocko
2018-03-01 13:55     ` Michal Hocko
2018-03-02  7:15     ` Aaron Lu
2018-03-02  7:15       ` Aaron Lu
2018-03-02 15:34       ` Dave Hansen
2018-03-02 15:34         ` Dave Hansen
2018-03-02  7:31     ` Huang, Ying
2018-03-02  7:31       ` Huang, Ying
2018-03-02  0:01   ` Andrew Morton
2018-03-02  0:01     ` Andrew Morton
2018-03-02  8:01     ` Aaron Lu
2018-03-02  8:01       ` Aaron Lu
2018-03-02 21:23       ` Andrew Morton
2018-03-02 21:23         ` Andrew Morton
2018-03-02 21:25         ` Dave Hansen
2018-03-02 21:25           ` Dave Hansen
2018-03-12 14:22   ` Vlastimil Babka
2018-03-13  3:34     ` Aaron Lu
2018-03-22 15:17       ` Matthew Wilcox
2018-03-26  3:03         ` Aaron Lu
2018-03-01  6:28 ` [PATCH v4 3/3] mm/free_pcppages_bulk: prefetch buddy while not holding lock Aaron Lu
2018-03-01  6:28   ` Aaron Lu
2018-03-01 14:00   ` Michal Hocko
2018-03-01 14:00     ` Michal Hocko
2018-03-02  8:31     ` Aaron Lu
2018-03-02  8:31       ` Aaron Lu
2018-03-02 17:55     ` Vlastimil Babka
2018-03-02 17:55       ` Vlastimil Babka
2018-03-02 18:00       ` Dave Hansen
2018-03-02 18:00         ` Dave Hansen
2018-03-02 18:08         ` Vlastimil Babka [this message]
2018-03-02 18:08           ` Vlastimil Babka
2018-03-05 11:41       ` Aaron Lu
2018-03-05 11:41         ` Aaron Lu
2018-03-05 11:48         ` Aaron Lu
2018-03-05 11:48           ` Aaron Lu
2018-03-06  7:55         ` Vlastimil Babka
2018-03-06  7:55           ` Vlastimil Babka
2018-03-06 12:27           ` Aaron Lu
2018-03-06 12:27             ` Aaron Lu
2018-03-06 12:53             ` Matthew Wilcox
2018-03-06 12:53               ` Matthew Wilcox
2018-03-02  0:09   ` Andrew Morton
2018-03-02  0:09     ` Andrew Morton
2018-03-02  8:27     ` Aaron Lu
2018-03-02  8:27       ` Aaron Lu
2018-03-09  8:24       ` [PATCH v4 3/3 update] " Aaron Lu
2018-03-09 21:58         ` Andrew Morton
2018-03-10 14:46           ` Aaron Lu
2018-03-12 15:05           ` Vlastimil Babka
2018-03-12 17:32         ` Dave Hansen
2018-03-13  3:35           ` Aaron Lu
2018-03-13  7:04             ` Aaron Lu
2018-03-20  9:50               ` Vlastimil Babka
2018-03-20 11:31                 ` [PATCH v4 3/3 update2] " Aaron Lu

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