From: Ard Biesheuvel <ardb@kernel.org>
To: Mark Rutland <mark.rutland@arm.com>
Cc: Peter Zijlstra <peterz@infradead.org>,
Steven Rostedt <rostedt@goodmis.org>, X86 ML <x86@kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Josh Poimboeuf <jpoimboe@redhat.com>,
Christophe Leroy <christophe.leroy@csgroup.eu>,
"Naveen N . Rao" <naveen.n.rao@linux.vnet.ibm.com>,
Miroslav Benes <mbenes@suse.cz>,
Nathan Chancellor <nathan@kernel.org>,
Nick Desaulniers <ndesaulniers@google.com>
Subject: Re: [RFC][PATCH] ftrace,objtool: PC32 based __mcount_loc
Date: Tue, 21 Jun 2022 18:27:39 +0200 [thread overview]
Message-ID: <CAMj1kXFuPAUfknadWDXPDXA5LYFnr0MGeXvF5MAYJBLxfCWEWw@mail.gmail.com> (raw)
In-Reply-To: <YqxoEJG6jGDWitg3@FVFF77S0Q05N>
On Fri, 17 Jun 2022 at 13:40, Mark Rutland <mark.rutland@arm.com> wrote:
>
> On Fri, Jun 17, 2022 at 01:24:53PM +0200, Peter Zijlstra wrote:
> >
> > Hi,
> >
> > I recently noticed that __mcount_loc is 64bit wide, containing absolute
> > addresses. Since __mcount_loc is a permanent section (not one we drop
> > after boot), this bloats the kernel memory usage for no real purpose.
> >
> > The below patch adds __mcount_loc_32 and objtool support to generate it.
> > This saves, on an x86_64-defconfig + FTRACE, 23975*4 ~= 94K of permanent
> > storage.
>
> We have a similar issue on arm64, which is exacerbated by needing ABS64
> relocations (24 bytes per entry!) adding significant bloat when FTRACE is
> enabled.
>
> It'd be really nice if going forwards compilers could expose an option to
> generate PC32/PREL32 entries directly for this.
>
As opposed to generating absolute references today? Or as opposed to
having to rely on our own tooling?
next prev parent reply other threads:[~2022-06-21 16:28 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-06-17 11:24 [RFC][PATCH] ftrace,objtool: PC32 based __mcount_loc Peter Zijlstra
2022-06-17 11:40 ` Mark Rutland
2022-06-21 16:27 ` Ard Biesheuvel [this message]
2022-06-23 14:19 ` Mark Rutland
2022-06-22 14:54 ` Steven Rostedt
2022-06-23 14:21 ` Mark Rutland
2022-06-24 0:01 ` Steven Rostedt
2022-06-17 11:44 ` Christophe Leroy
2022-06-17 12:06 ` Peter Zijlstra
2022-06-17 20:11 ` Josh Poimboeuf
2022-06-20 7:35 ` Peter Zijlstra
2022-06-20 7:42 ` Christophe Leroy
2022-06-22 14:50 ` Steven Rostedt
2022-06-24 7:16 ` Peter Zijlstra
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=CAMj1kXFuPAUfknadWDXPDXA5LYFnr0MGeXvF5MAYJBLxfCWEWw@mail.gmail.com \
--to=ardb@kernel.org \
--cc=christophe.leroy@csgroup.eu \
--cc=jpoimboe@redhat.com \
--cc=linux-kernel@vger.kernel.org \
--cc=mark.rutland@arm.com \
--cc=mbenes@suse.cz \
--cc=nathan@kernel.org \
--cc=naveen.n.rao@linux.vnet.ibm.com \
--cc=ndesaulniers@google.com \
--cc=peterz@infradead.org \
--cc=rostedt@goodmis.org \
--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 an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.