From: Andre Przywara <andre.przywara@arm.com>
To: Grygorii Strashko <grygorii.strashko@ti.com>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
linux-rt-users@vger.kernel.org,
Linux ARM Mailing List <linux-arm-kernel@lists.infradead.org>,
linux-kernel@vger.kernel.org
Subject: Re: arm64 + ARM64_64K_PAGES=y
Date: Mon, 12 Nov 2018 14:27:03 +0000 [thread overview]
Message-ID: <20181112142703.0d6ceb57@donnerap.cambridge.arm.com> (raw)
In-Reply-To: <274c9742-0aa9-b4a5-11cb-b506aeef7761@ti.com>
On Fri, 9 Nov 2018 13:15:47 -0600
Grygorii Strashko <grygorii.strashko@ti.com> wrote:
Hi,
> On 11/8/18 12:14 PM, Grygorii Strashko wrote:
> >
> >
> > On 11/8/18 6:00 AM, Sebastian Andrzej Siewior wrote:
> >> On 2018-11-06 15:34:55 [-0600], Grygorii Strashko wrote:
> >>> Hi All,
> >> Hi,
> >>
> >>> Do anybody tried to use ARM64 RT with 76K pages enabled?
> >>
> >> 75 would be an off by one but this :)
> >
> > Ops 8-). at least subj is correct.
> >
> >>
> >>> My attempt shows that enabling CONFIG_ARM64_64K_PAGES=y
> >>> increases latencies by ~30%
That's not really surprising. Performance on systems using a bigger page
size granules might have some trade-offs (bigger memory overhead, worse
cache utilization), so 64K pages might not be really great for your
particular workload. You would probably need a real performance
analysis (using perf, for instance) to pinpoint TLB misses as your
bottleneck.
> >>> cyclictest -n -m -Sp98 -q -D2m with =y
> >>>
> >>>
> >>> T: 0 ( 772) P:98 I:1000 C: 120000 Min: 7 Act: 13 Avg:
> >>> 10 Max: 85 T: 1 ( 773) P:98 I:1500 C: 79998 Min: 7
> >>> Act: 13 Avg: 10 Max: 71 T: 2 ( 774) P:98 I:2000 C:
> >>> 59997 Min: 7 Act: 11 Avg: 11 Max: 64 T: 3 ( 775)
> >>> P:98 I:2500 C: 47996 Min: 7 Act: 14 Avg: 12 Max: 66
> >>>
> >>>
> >>> cyclictest -n -m -Sp98 -q -D2m with CONFIG_ARM64_64K_PAGES=n
> >>>
> >>>
> >>> T: 0 ( 697) P:98 I:1000 C: 120000 Min: 7 Act: 10 Avg:
> >>> 9 Max: 38 T: 1 ( 698) P:98 I:1500 C: 79987 Min: 7
> >>> Act: 10 Avg: 10 Max: 32 T: 2 ( 699) P:98 I:2000 C:
> >>> 59981 Min: 7 Act: 14 Avg: 11 Max: 46 T: 3 ( 700)
> >>> P:98 I:2500 C: 47977 Min: 6 Act: 11 Avg: 10 Max:
> >>> 45
> >>
> >> So this is an idle system?
> >
> > Yes (in general) - it's collected with systemd, so some daemons are
> > active.
> >> The Kconfig help says "faster TLB lookup". Interesting.
> >> Are the 16k pages in between (latency wise) by any chance?
> >
> > I'll try it.
>
> no i'll not, at least not fast. with 16k pages enabled I can't boot
> TI 4.14 kernel
> - 4.14.71-rt44.
> No msg in log, just "Starting kernel ..."
You need a core that actually supports 16K pages (supporting
certain page size granules is architecturally optional).
From the Arm Ltd. cores it's Cortex-A73, A75 or A55, possibly other
newer ones as well. Cortex-A53, A57 and A72 do not support 16k pages.
Cheers,
Andre.
next prev parent reply other threads:[~2018-11-12 14:27 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-11-06 21:34 arm64 + ARM64_64K_PAGES=y Grygorii Strashko
2018-11-08 12:00 ` Sebastian Andrzej Siewior
2018-11-08 18:14 ` Grygorii Strashko
2018-11-09 19:15 ` Grygorii Strashko
2018-11-12 14:27 ` Andre Przywara [this message]
2018-11-12 21:22 ` Grygorii Strashko
2018-11-09 4:42 ` Anshuman Khandual
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=20181112142703.0d6ceb57@donnerap.cambridge.arm.com \
--to=andre.przywara@arm.com \
--cc=bigeasy@linutronix.de \
--cc=grygorii.strashko@ti.com \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-rt-users@vger.kernel.org \
/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).