From: Daniel Wagner <dwagner@suse.de>
To: Uladzislau Rezki <urezki@gmail.com>
Cc: 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 08:05:39 +0200 [thread overview]
Message-ID: <20191009060539.fmpqesc4wfisulrl@beryllium.lan> (raw)
In-Reply-To: <20191008160459.GA5487@pc636>
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? :)
Thanks,
Daniel
next prev parent reply other threads:[~2019-10-09 6:05 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 [this message]
2019-10-09 9:47 ` Uladzislau Rezki
2019-10-07 8:27 ` Daniel Wagner
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=20191009060539.fmpqesc4wfisulrl@beryllium.lan \
--to=dwagner@suse.de \
--cc=akpm@linux-foundation.org \
--cc=bigeasy@linutronix.de \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=linux-rt-users@vger.kernel.org \
--cc=urezki@gmail.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 a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).