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From: Peter Zijlstra <peterz@infradead.org>
To: "Huang, Ying" <ying.huang@intel.com>
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org,
	Andrew Morton <akpm@linux-foundation.org>,
	Michal Hocko <mhocko@suse.com>, Rik van Riel <riel@redhat.com>,
	Mel Gorman <mgorman@suse.de>, Ingo Molnar <mingo@kernel.org>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	Dan Williams <dan.j.williams@intel.com>,
	Fengguang Wu <fengguang.wu@intel.com>
Subject: Re: [RFC 08/10] autonuma, memory tiering: Select hotter pages to promote to fast memory node
Date: Mon, 4 Nov 2019 09:44:04 +0100	[thread overview]
Message-ID: <20191104084404.GA4131@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <87k18gcqih.fsf@yhuang-dev.intel.com>

On Mon, Nov 04, 2019 at 10:41:10AM +0800, Huang, Ying wrote:

> >> +#define NUMA_SCAN_NR_HIST	16
> >> +		int numa_scan_idx;
> >> +		unsigned long numa_scan_jiffies[NUMA_SCAN_NR_HIST];
> >> +		unsigned long numa_scan_starts[NUMA_SCAN_NR_HIST];
> >
> > Why 16? This is 4 cachelines.
> 
> We want to keep the NUMA scanning history reasonably long.  From
> task_scan_min(), the minimal interval between task_numa_work() running
> is about 100 ms by default.  So we can keep 1600 ms history by default
> if NUMA_SCAN_NR_HIST is 16.  If user choose to use smaller
> sysctl_numa_balancing_scan_size, then we can only keep shorter history.
> In general, we want to keep no less than 1000 ms history.  So 16 appears
> like a reasonable choice for us.  Any other suggestion?

This is very good information for Changelogs and comments :-)

  reply	other threads:[~2019-11-04  8:44 UTC|newest]

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-11-01  7:57 [RFC 00/10] autonuma: Optimize memory placement in memory tiering system Huang, Ying
2019-11-01  7:57 ` [RFC 01/10] autonuma: Fix watermark checking in migrate_balanced_pgdat() Huang, Ying
2019-11-01 11:11   ` Mel Gorman
2019-11-01  7:57 ` [RFC 02/10] autonuma: Reduce cache footprint when scanning page tables Huang, Ying
2019-11-01 11:13   ` Mel Gorman
2019-11-01  7:57 ` [RFC 03/10] autonuma: Add NUMA_BALANCING_MEMORY_TIERING mode Huang, Ying
2019-11-01  7:57 ` [RFC 04/10] autonuma, memory tiering: Rate limit NUMA migration throughput Huang, Ying
2019-11-01  7:57 ` [RFC 05/10] autonuma, memory tiering: Use kswapd to demote cold pages to PMEM Huang, Ying
2019-11-01  7:57 ` [RFC 06/10] autonuma, memory tiering: Skip to scan fastest memory Huang, Ying
2019-11-01  7:57 ` [RFC 07/10] autonuma, memory tiering: Only promote page if accessed twice Huang, Ying
2019-11-01  7:57 ` [RFC 08/10] autonuma, memory tiering: Select hotter pages to promote to fast memory node Huang, Ying
2019-11-01  9:24   ` Peter Zijlstra
2019-11-04  2:41     ` Huang, Ying
2019-11-04  8:44       ` Peter Zijlstra [this message]
2019-11-04 10:13         ` Huang, Ying
2019-11-01  7:57 ` [RFC 09/10] autonuma, memory tiering: Double hot threshold for write hint page fault Huang, Ying
2019-11-01  7:57 ` [RFC 10/10] autonuma, memory tiering: Adjust hot threshold automatically Huang, Ying
2019-11-01  9:31   ` Peter Zijlstra
2019-11-04  6:11     ` Huang, Ying
2019-11-04  8:49       ` Peter Zijlstra
2019-11-04 10:12         ` Huang, Ying
2019-11-21  8:38         ` Huang, Ying

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