From: Peter Zijlstra <peterz@infradead.org>
To: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
linux-arm-kernel <linux-arm-kernel@lists.infradead.org>,
the arch/x86 maintainers <x86@kernel.org>,
Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will.deacon@arm.com>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Arnd Bergmann <arnd@arndb.de>,
Steven Rostedt <rostedt@goodmis.org>
Subject: Re: [PATCH 2/5] kernel/jump_label: implement generic support for relative references
Date: Thu, 28 Jun 2018 11:37:38 +0200 [thread overview]
Message-ID: <20180628093738.GE2494@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <CAKv+Gu-bL0neh61=1B=Dja7+tsH_ong731t2Xp17h4E1fjavjA@mail.gmail.com>
On Thu, Jun 28, 2018 at 11:29:40AM +0200, Ard Biesheuvel wrote:
> On 28 June 2018 at 11:25, Peter Zijlstra <peterz@infradead.org> wrote:
> >> > Meh. I thought IS_ENABLED() was preferred over #ifdef, no?
> >
> > Dunno, I just reacted to the proposed code's uglyness :-)
> >
>
> I will try to come up with something that rhymes, ok? :-)
:-)
> >> ... and it means the sort() routine will unconditionally perform an
> >> indirect function call even if the arch does not require it.
> >
> > Yeah, not sure I care about that here, this is a one time affair, very
> > far away from any fast paths.
> >
>
> Fair enough.
I recently had thoughts about doing the sort at link time, but then I
figured I didn't care enough to go write the tool to do that. The reason
was in that other patch-set that might conflict, that wants to use jump
labels _very_ early (for x86), so we had to lift the ideal nops stuff
and the cpu feature bits it relies upon to early code.
All in all the patch wasn't terrible and that made me completely loose
interest about doing the link-time thing again.
However, if someone is 'concerned' about the boot time performance, and
figures avoiding the sort is somehow worth it, they can look into it.
next prev parent reply other threads:[~2018-06-28 9:37 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-06-27 16:05 [PATCH 0/5] add support for relative references in jump tables Ard Biesheuvel
2018-06-27 16:06 ` [PATCH 1/5] kernel/jump_label: abstract jump_entry member accessors Ard Biesheuvel
2018-06-28 8:40 ` Peter Zijlstra
2018-06-27 16:06 ` [PATCH 2/5] kernel/jump_label: implement generic support for relative references Ard Biesheuvel
2018-06-28 8:50 ` Peter Zijlstra
2018-06-28 9:02 ` Ard Biesheuvel
2018-06-28 9:04 ` Ard Biesheuvel
2018-06-28 9:25 ` Peter Zijlstra
2018-06-28 9:29 ` Ard Biesheuvel
2018-06-28 9:37 ` Peter Zijlstra [this message]
2018-06-27 16:06 ` [PATCH 3/5] arm64/kernel: jump_label: switch to " Ard Biesheuvel
2018-06-28 9:17 ` Will Deacon
2018-06-27 16:06 ` [PATCH 4/5] x86: jump_label: switch to jump_entry accessors Ard Biesheuvel
2018-06-28 9:11 ` Peter Zijlstra
2018-06-28 9:14 ` Ard Biesheuvel
2018-06-27 16:06 ` [PATCH 5/5] x86/kernel: jump_table: use relative references Ard Biesheuvel
2018-06-28 8:31 ` Peter Zijlstra
2018-06-28 8:34 ` Ard Biesheuvel
2018-06-28 9:28 ` Peter Zijlstra
2018-07-02 5:14 ` [lkp-robot] [x86/kernel] b1ff47aace: WARNING:at_kernel/jump_label.c:#__jump_label_update kernel test robot
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=20180628093738.GE2494@hirez.programming.kicks-ass.net \
--to=peterz@infradead.org \
--cc=ard.biesheuvel@linaro.org \
--cc=arnd@arndb.de \
--cc=catalin.marinas@arm.com \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-kernel@vger.kernel.org \
--cc=mingo@redhat.com \
--cc=rostedt@goodmis.org \
--cc=tglx@linutronix.de \
--cc=will.deacon@arm.com \
--cc=x86@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).