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From: Marcelo Tosatti <mtosatti@redhat.com>
To: Nicolas Saenz Julienne <nsaenzju@redhat.com>
Cc: Minchan Kim <minchan@kernel.org>,
	Mel Gorman <mgorman@techsingularity.net>,
	Vlastimil Babka <vbabka@suse.cz>,
	Michal Hocko <mhocko@kernel.org>,
	LKML <linux-kernel@vger.kernel.org>,
	Linux-MM <linux-mm@kvack.org>
Subject: Re: [RFC PATCH 0/6] Drain remote per-cpu directly
Date: Wed, 27 Apr 2022 12:21:47 -0300	[thread overview]
Message-ID: <Ymlfi2vas76Tgk4W@fuller.cnet> (raw)
In-Reply-To: <cf861ff3bf106b71994886cad7c4570b6ce9af0d.camel@redhat.com>

On Tue, Apr 26, 2022 at 01:06:12PM +0200, Nicolas Saenz Julienne wrote:
> On Mon, 2022-04-25 at 15:58 -0700, Minchan Kim wrote:
> > On Wed, Apr 20, 2022 at 10:59:00AM +0100, Mel Gorman wrote:
> > > This series has the same intent as Nicolas' series "mm/page_alloc: Remote
> > > per-cpu lists drain support" -- avoid interference of a high priority
> > > task due to a workqueue item draining per-cpu page lists. While many
> > > workloads can tolerate a brief interruption, it may be cause a real-time
> > > task runnning on a NOHZ_FULL CPU to miss a deadline and at minimum,
> > > the draining in non-deterministic.
> > 
> > Yeah, the non-deterministic is a problem. I saw the kworker-based draining
> > takes 100+ms(up to 300ms observed) sometimes in alloc_contig_range if CPUs
> > are heavily loaded.
> > 
> > I am not sure Nicolas already observed. it's not only problem of
> > per_cpu_pages but it is also lru_pvecs (pagevec) draining.
> > Do we need to introduce similar(allow remote drainning with spin_lock)
> > solution for pagevec?
> 
> Yes, I'm aware of the lru problem. I'll start working on it too once we're done
> with the page allocator (and if no-one beats me to it). That said, I don't know
> if we can apply the exact same approach, the devil is in the details. :)

I think one necessary step for that (adding spinlock to protect per-CPU
lru_pvecs) would be to find a suitable testcase.

Mel, do you have anything in mind ?



> 
> -- 
> Nicolás Sáenz
> 
> 


  reply	other threads:[~2022-04-27 15:22 UTC|newest]

Thread overview: 21+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-04-20  9:59 [RFC PATCH 0/6] Drain remote per-cpu directly Mel Gorman
2022-04-20  9:59 ` [PATCH 1/6] mm/page_alloc: Add page->buddy_list and page->pcp_list Mel Gorman
2022-04-20 20:43   ` Matthew Wilcox
2022-04-21  8:38     ` Mel Gorman
2022-04-20  9:59 ` [PATCH 2/6] mm/page_alloc: Use only one PCP list for THP-sized allocations Mel Gorman
2022-04-20  9:59 ` [PATCH 3/6] mm/page_alloc: Split out buddy removal code from rmqueue into separate helper Mel Gorman
2022-04-20  9:59 ` [PATCH 4/6] mm/page_alloc: Remove unnecessary page == NULL check in rmqueue Mel Gorman
2022-04-20  9:59 ` [PATCH 5/6] mm/page_alloc: Protect PCP lists with a spinlock Mel Gorman
2022-04-20 14:02   ` Hillf Danton
2022-04-20 14:35     ` Nicolas Saenz Julienne
2022-04-26 16:42   ` Nicolas Saenz Julienne
2022-04-26 16:48     ` Vlastimil Babka
2022-04-29  9:13     ` Mel Gorman
2022-04-26 19:24   ` Minchan Kim
2022-04-29  9:05     ` Mel Gorman
2022-04-20  9:59 ` [PATCH 6/6] mm/page_alloc: Remotely drain per-cpu lists Mel Gorman
2022-04-25 22:58 ` [RFC PATCH 0/6] Drain remote per-cpu directly Minchan Kim
2022-04-26 11:06   ` Nicolas Saenz Julienne
2022-04-27 15:21     ` Marcelo Tosatti [this message]
2022-04-26  2:49 ` Suren Baghdasaryan
2022-04-26  6:30   ` Suren Baghdasaryan

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