All of lore.kernel.org
 help / color / mirror / Atom feed
From: Dave Hansen <dave.hansen@intel.com>
To: Aaron Lu <aaron.lu@intel.com>, Michal Hocko <mhocko@kernel.org>
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>, Vlastimil Babka <vbabka@suse.cz>,
	Mel Gorman <mgorman@techsingularity.net>,
	Matthew Wilcox <willy@infradead.org>,
	David Rientjes <rientjes@google.com>
Subject: Re: [PATCH v4 2/3] mm/free_pcppages_bulk: do not hold lock when picking pages to free
Date: Fri, 2 Mar 2018 07:34:01 -0800	[thread overview]
Message-ID: <aa14d724-525c-7532-2e8e-6c4c6094e03f@intel.com> (raw)
In-Reply-To: <20180302071533.GA6356@intel.com>

On 03/01/2018 11:15 PM, Aaron Lu wrote:
> 
>> I am still quite surprised that this would have such a large impact.
> Most likely due to the cachelines for these page structures are warmed
> up outside of zone->lock.

The workload here is a pretty tight microbenchmark and single biggest
bottleneck is cache misses on 'struct page'.  It's not memory bandwidth
bound.  So, anything you can give the CPU keep it fed and not waiting on
cache misses will be a win.

There's never going to be a real-world workload that sees this kind of
increase, but the change in the micro isn't super-surprising because it
so directly targets the bottleneck.

WARNING: multiple messages have this Message-ID (diff)
From: Dave Hansen <dave.hansen@intel.com>
To: Aaron Lu <aaron.lu@intel.com>, Michal Hocko <mhocko@kernel.org>
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>, Vlastimil Babka <vbabka@suse.cz>,
	Mel Gorman <mgorman@techsingularity.net>,
	Matthew Wilcox <willy@infradead.org>,
	David Rientjes <rientjes@google.com>
Subject: Re: [PATCH v4 2/3] mm/free_pcppages_bulk: do not hold lock when picking pages to free
Date: Fri, 2 Mar 2018 07:34:01 -0800	[thread overview]
Message-ID: <aa14d724-525c-7532-2e8e-6c4c6094e03f@intel.com> (raw)
In-Reply-To: <20180302071533.GA6356@intel.com>

On 03/01/2018 11:15 PM, Aaron Lu wrote:
> 
>> I am still quite surprised that this would have such a large impact.
> Most likely due to the cachelines for these page structures are warmed
> up outside of zone->lock.

The workload here is a pretty tight microbenchmark and single biggest
bottleneck is cache misses on 'struct page'.  It's not memory bandwidth
bound.  So, anything you can give the CPU keep it fed and not waiting on
cache misses will be a win.

There's never going to be a real-world workload that sees this kind of
increase, but the change in the micro isn't super-surprising because it
so directly targets the bottleneck.

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>

  reply	other threads:[~2018-03-02 15:34 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 [this message]
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
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

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=aa14d724-525c-7532-2e8e-6c4c6094e03f@intel.com \
    --to=dave.hansen@intel.com \
    --cc=aaron.lu@intel.com \
    --cc=ak@linux.intel.com \
    --cc=akpm@linux-foundation.org \
    --cc=kemi.wang@intel.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-mm@kvack.org \
    --cc=mgorman@techsingularity.net \
    --cc=mhocko@kernel.org \
    --cc=rientjes@google.com \
    --cc=tim.c.chen@linux.intel.com \
    --cc=vbabka@suse.cz \
    --cc=willy@infradead.org \
    --cc=ying.huang@intel.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.