From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To: Arnd Bergmann <arnd@kernel.org>
Cc: linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org, Arnd Bergmann <arnd@arndb.de>,
linux-mm@kvack.org, linux-rt-devel@lists.linux.dev,
Ard Biesheuvel <ardb@kernel.org>,
Clark Williams <clrkwllms@kernel.org>,
Jason Baron <jbaron@akamai.com>,
Josh Poimboeuf <jpoimboe@kernel.org>,
Linus Walleij <linus.walleij@linaro.org>,
Mark Rutland <mark.rutland@arm.com>,
Matthew Wilcox <willy@infradead.org>,
Peter Zijlstra <peterz@infradead.org>,
Russell King <linux@armlinux.org.uk>,
Steven Rostedt <rostedt@goodmis.org>
Subject: Re: [PATCH 2/4] ARM: Disable HIGHPTE on PREEMPT_RT kernels
Date: Wed, 11 Dec 2024 15:04:02 +0100 [thread overview]
Message-ID: <20241211140402.yf7gMExr@linutronix.de> (raw)
In-Reply-To: <20241211134811.wM_UADhQ@linutronix.de>
On 2024-12-11 14:48:11 [+0100], To Arnd Bergmann wrote:
> I guess if you have boxes with 4GiB+ and can proof that the performance
> improves without HIGHPTE (since you don't have to map the page table).
> The question is then how much of low mem has to be used instead and when
> does it start to hurt.
Some numbers have been been documented in commit
14315592009c1 ("x86, mm: Allow highmem user page tables to be disabled at boot time")
and I would like cite:
| We could probably handwave up an argument for a threshold at 16G of total
| RAM.
which means HIGHPTE would make sense with >= 16GiB of memory.
Sebastian
next prev parent reply other threads:[~2024-12-11 14:04 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-12-10 16:05 [PATCH 0/4] ARM: towards 32-bit preempt-rt support Arnd Bergmann
2024-12-10 16:05 ` [PATCH 1/4] ARM: Disable jump-label on PREEMPT_RT Arnd Bergmann
2024-12-11 13:04 ` Linus Walleij
2024-12-11 13:26 ` Sebastian Andrzej Siewior
2024-12-10 16:05 ` [PATCH 2/4] ARM: Disable HIGHPTE on PREEMPT_RT kernels Arnd Bergmann
2024-12-11 13:29 ` Linus Walleij
2024-12-11 15:22 ` Sebastian Andrzej Siewior
2024-12-13 0:27 ` Linus Walleij
2024-12-13 9:11 ` Russell King (Oracle)
2024-12-14 22:11 ` Matthew Wilcox
2024-12-11 13:48 ` Sebastian Andrzej Siewior
2024-12-11 14:04 ` Sebastian Andrzej Siewior [this message]
2024-12-11 14:30 ` Arnd Bergmann
2024-12-11 15:55 ` Russell King (Oracle)
2024-12-20 14:37 ` Arnd Bergmann
2024-12-10 16:05 ` [PATCH 3/4] ARM: drop CONFIG_HIGHPTE support Arnd Bergmann
2024-12-11 13:32 ` Linus Walleij
2024-12-11 13:50 ` Russell King (Oracle)
2024-12-11 14:31 ` Linus Walleij
2024-12-11 14:25 ` Sebastian Andrzej Siewior
2024-12-14 18:40 ` David Laight
2024-12-20 13:10 ` Linus Walleij
2024-12-20 14:30 ` Arnd Bergmann
2024-12-10 16:05 ` [PATCH 4/4] mm: drop HIGHPTE support altogether Arnd Bergmann
2024-12-11 13:53 ` Linus Walleij
2024-12-11 14:29 ` Sebastian Andrzej Siewior
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=20241211140402.yf7gMExr@linutronix.de \
--to=bigeasy@linutronix.de \
--cc=ardb@kernel.org \
--cc=arnd@arndb.de \
--cc=arnd@kernel.org \
--cc=clrkwllms@kernel.org \
--cc=jbaron@akamai.com \
--cc=jpoimboe@kernel.org \
--cc=linus.walleij@linaro.org \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=linux-rt-devel@lists.linux.dev \
--cc=linux@armlinux.org.uk \
--cc=mark.rutland@arm.com \
--cc=peterz@infradead.org \
--cc=rostedt@goodmis.org \
--cc=willy@infradead.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