From: Christophe Leroy <christophe.leroy@c-s.fr>
To: Christoph Hellwig <hch@infradead.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Paul Mackerras <paulus@samba.org>,
Michael Ellerman <mpe@ellerman.id.au>,
linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v5] powerpc/irq: inline call_do_irq() and call_do_softirq() on PPC32
Date: Thu, 12 Dec 2019 17:34:46 +0100 [thread overview]
Message-ID: <878e4ac8-9bfa-394d-8bca-f09a78f54904@c-s.fr> (raw)
In-Reply-To: <20191212125222.GB3381@infradead.org>
Le 12/12/2019 à 13:52, Christoph Hellwig a écrit :
> On Sat, Dec 07, 2019 at 05:20:04PM +0000, Christophe Leroy wrote:
>> call_do_irq() and call_do_softirq() are simple enough to be
>> worth inlining.
>>
>> Inlining them avoids an mflr/mtlr pair plus a save/reload on stack.
>> It also allows GCC to keep the saved ksp_limit in an nonvolatile reg.
>>
>> This is inspired from S390 arch. Several other arches do more or
>> less the same. The way sparc arch does seems odd thought.
>
> Any reason you only do this for 32-bit and not 64-bit as well?
>
Yes ... There has been a long discussion on this in v4, see
https://patchwork.ozlabs.org/patch/1174288/
The problem is that on PPC64, r2 register is used as TOC pointer and it
is apparently not straithforward to make sure the caller and the callee
are using the same TOC.
On PPC32 it's more simple, r2 is current task_struct at all time, it
never changes.
Christophe
next prev parent reply other threads:[~2019-12-12 16:34 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-12-07 17:20 [PATCH v5] powerpc/irq: inline call_do_irq() and call_do_softirq() on PPC32 Christophe Leroy
2019-12-12 12:52 ` Christoph Hellwig
2019-12-12 16:34 ` Christophe Leroy [this message]
2020-06-01 7:26 ` Christophe Leroy
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=878e4ac8-9bfa-394d-8bca-f09a78f54904@c-s.fr \
--to=christophe.leroy@c-s.fr \
--cc=benh@kernel.crashing.org \
--cc=hch@infradead.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linuxppc-dev@lists.ozlabs.org \
--cc=mpe@ellerman.id.au \
--cc=paulus@samba.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).