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 [thread overview]
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
next prev parent reply other threads:[~2019-10-09 9:47 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-03 9:09 [PATCH] mm: vmalloc: Use the vmap_area_lock to protect ne_fit_preload_node 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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