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From: Uladzislau Rezki <urezki@gmail.com>
To: Daniel Wagner <dwagner@suse.de>
Cc: Uladzislau Rezki <urezki@gmail.com>,
	Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
	linux-mm@kvack.org, linux-kernel@vger.kernel.org,
	linux-rt-users@vger.kernel.org,
	Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [PATCH] mm: vmalloc: Use the vmap_area_lock to protect ne_fit_preload_node
Date: Wed, 9 Oct 2019 11:47:14 +0200
Message-ID: <20191009094714.GA7343@pc636> (raw)
In-Reply-To: <20191009060539.fmpqesc4wfisulrl@beryllium.lan>

Hello, Daniel.

On Wed, Oct 09, 2019 at 08:05:39AM +0200, Daniel Wagner wrote:
> On Tue, Oct 08, 2019 at 06:04:59PM +0200, Uladzislau Rezki wrote:
> > > so, we do not guarantee, instead we minimize number of allocations
> > > with GFP_NOWAIT flag. For example on my 4xCPUs i am not able to
> > > even trigger the case when CPU is not preloaded.
> > > 
> > > I can test it tomorrow on my 12xCPUs to see its behavior there.
> > > 
> > Tested it on different systems. For example on my 8xCPUs system that
> > runs PREEMPT kernel i see only few GFP_NOWAIT allocations, i.e. it
> > happens when we land to another CPU that was not preloaded.
> > 
> > I run the special test case that follows the preload pattern and path.
> > So 20 "unbind" threads run it and each does 1000000 allocations. As a
> > result only 3.5 times among 1000000, during splitting, CPU was not
> > preloaded thus, GFP_NOWAIT was used to obtain an extra object.
> > 
> > It is obvious that slightly modified approach still minimizes allocations
> > in atomic context, so it can happen but the number is negligible and can
> > be ignored, i think.
> 
> Thanks for doing the tests. In this case I would suggest to get rid of
> the preempt_disable() micro optimization, since there is almost no
> gain in doing so. Do you send a patch? :)
> 
I can do it, for sure, in case you do not mind, since it was your
initiative. Otherwise you can upload v2.

--
Vlad Rezki

  reply index

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-03  9:09 Daniel Wagner
2019-10-03 11:55 ` Uladzislau Rezki
2019-10-04 15:37 ` Sebastian Andrzej Siewior
2019-10-04 16:20   ` Uladzislau Rezki
2019-10-04 16:30     ` Sebastian Andrzej Siewior
2019-10-04 17:04       ` Uladzislau Rezki
2019-10-04 17:45         ` Sebastian Andrzej Siewior
2019-10-07  8:30       ` Daniel Wagner
2019-10-07 10:56         ` Sebastian Andrzej Siewior
2019-10-07 16:23           ` Uladzislau Rezki
2019-10-07 16:34             ` Daniel Wagner
2019-10-07 16:56               ` Uladzislau Rezki
2019-10-07 17:22                 ` Daniel Wagner
2019-10-07 17:36                 ` Sebastian Andrzej Siewior
2019-10-07 21:44                   ` Uladzislau Rezki
2019-10-08 16:04                     ` Uladzislau Rezki
2019-10-09  6:05                       ` Daniel Wagner
2019-10-09  9:47                         ` Uladzislau Rezki [this message]
2019-10-07  8:27   ` Daniel Wagner

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