From: Andi Kleen <andi-Vw/NltI1exuRpAAqCnN02g@public.gmane.org>
To: Mathieu Desnoyers
<mathieu.desnoyers-vg+e7yoeK/dWk0Htik3J/w@public.gmane.org>
Cc: "Paul E. McKenney"
<paulmck-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org>,
Boqun Feng <boqun.feng-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>,
Peter Zijlstra <peterz-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>,
Paul Turner <pjt-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>,
Andrew Hunter <ahh-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>,
Andy Lutomirski <luto-kltTT9wpgjJwATOyAt5JVQ@public.gmane.org>,
Dave Watson <davejwatson-b10kYP2dOMg@public.gmane.org>,
Josh Triplett <josh-iaAMLnmF4UmaiuxdJuQwMA@public.gmane.org>,
Will Deacon <will.deacon-5wv7dgnIgG8@public.gmane.org>,
linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
Thomas Gleixner <tglx-hfZtesqFncYOwBW4kG4KsQ@public.gmane.org>,
Andi Kleen <andi-Vw/NltI1exuRpAAqCnN02g@public.gmane.org>,
Chris Lameter <cl-vYTEC60ixJUAvxtiuMwx3w@public.gmane.org>,
Ingo Molnar <mingo-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>,
"H. Peter Anvin" <hpa-YMNOUZJC4hwAvxtiuMwx3w@public.gmane.org>,
Ben Maurer <bmaurer-b10kYP2dOMg@public.gmane.org>,
Steven Rostedt <rostedt-nx8X9YLhiw1AfugRpC6u6w@public.gmane.org>,
Linus Torvalds
<torvalds-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>,
Andrew Morton
<akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>,
Russell King <linux-lFZ/pmaqli7XmaaqVzeoHQ@public.gmane.org>,
Catalin Marinas <catalin.marinas-5wv7dgnIgG8@public.gmane.org>
Subject: Re: [RFC PATCH for 4.15 09/14] Provide cpu_opv system call
Date: Fri, 13 Oct 2017 19:50:30 -0700 [thread overview]
Message-ID: <20171014025029.GL2482@two.firstfloor.org> (raw)
In-Reply-To: <20171012230326.19984-10-mathieu.desnoyers-vg+e7yoeK/dWk0Htik3J/w@public.gmane.org>
> + pagefault_disable();
> + switch (len) {
> + case 1:
> + if (__get_user(tmp._u8, (uint8_t __user *)p))
> + goto end;
> + tmp._u8 += (uint8_t)count;
> + if (__put_user(tmp._u8, (uint8_t __user *)p))
> + goto end;
> + break;
It seems the code size could be dramatically shrunk by using a function
pointer callback for the actual operation, and then avoiding all the
copies. Since this is only a fallback this shouldn't be a problem
(and modern branch predictors are fairly good in such situations anyways)
If you really want to keep the code it would be better if you used
some macros -- i bet there's a typo in here somewhere in this
forest.
-Andi
WARNING: multiple messages have this Message-ID (diff)
From: Andi Kleen <andi@firstfloor.org>
To: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
Boqun Feng <boqun.feng@gmail.com>,
Peter Zijlstra <peterz@infradead.org>,
Paul Turner <pjt@google.com>, Andrew Hunter <ahh@google.com>,
Andy Lutomirski <luto@amacapital.net>,
Dave Watson <davejwatson@fb.com>,
Josh Triplett <josh@joshtriplett.org>,
Will Deacon <will.deacon@arm.com>,
linux-kernel@vger.kernel.org,
Thomas Gleixner <tglx@linutronix.de>,
Andi Kleen <andi@firstfloor.org>, Chris Lameter <cl@linux.com>,
Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>,
Ben Maurer <bmaurer@fb.com>, Steven Rostedt <rostedt@goodmis.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
Andrew Morton <akpm@linux-foundation.org>,
Russell King <linux@arm.linux.org.uk>,
Catalin Marinas <catalin.marinas@arm.com>,
Michael Kerrisk <mtk.manpages@gmail.com>,
linux-api@vger.kernel.org
Subject: Re: [RFC PATCH for 4.15 09/14] Provide cpu_opv system call
Date: Fri, 13 Oct 2017 19:50:30 -0700 [thread overview]
Message-ID: <20171014025029.GL2482@two.firstfloor.org> (raw)
In-Reply-To: <20171012230326.19984-10-mathieu.desnoyers@efficios.com>
> + pagefault_disable();
> + switch (len) {
> + case 1:
> + if (__get_user(tmp._u8, (uint8_t __user *)p))
> + goto end;
> + tmp._u8 += (uint8_t)count;
> + if (__put_user(tmp._u8, (uint8_t __user *)p))
> + goto end;
> + break;
It seems the code size could be dramatically shrunk by using a function
pointer callback for the actual operation, and then avoiding all the
copies. Since this is only a fallback this shouldn't be a problem
(and modern branch predictors are fairly good in such situations anyways)
If you really want to keep the code it would be better if you used
some macros -- i bet there's a typo in here somewhere in this
forest.
-Andi
next prev parent reply other threads:[~2017-10-14 2:50 UTC|newest]
Thread overview: 113+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-10-12 23:03 [RFC PATCH v9 for 4.15 00/14] Restartable sequences and CPU op vector system calls Mathieu Desnoyers
2017-10-12 23:03 ` [RFC PATCH v9 for 4.15 01/14] Restartable sequences system call Mathieu Desnoyers
2017-10-13 0:36 ` Linus Torvalds
2017-10-13 0:36 ` Linus Torvalds
2017-10-13 9:35 ` Ben Maurer
2017-10-13 9:35 ` Ben Maurer
[not found] ` <DM5PR15MB1690DA99E4AA74FBE54CF7F9CF480-kTBAvIqET4EjX1lkf7hTyId3EbNNOtPMvxpqHgZTriW3zl9H0oFU5g@public.gmane.org>
2017-10-13 18:30 ` Linus Torvalds
2017-10-13 18:30 ` Linus Torvalds
[not found] ` <CA+55aFzPBES0JOYuZhuNM7NKN+G9ytZQT2daueFPw0j9HGpdGQ-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2017-10-13 20:54 ` Paul E. McKenney
2017-10-13 20:54 ` Paul E. McKenney
[not found] ` <20171013205418.GM3521-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org>
2017-10-13 21:05 ` Linus Torvalds
2017-10-13 21:05 ` Linus Torvalds
[not found] ` <CA+55aFwvNS95ByZJTh1yG25QfaD0K0ZByK3iXeeRU8LafFiGFQ-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2017-10-13 21:21 ` Paul E. McKenney
2017-10-13 21:21 ` Paul E. McKenney
2017-10-13 21:36 ` Mathieu Desnoyers
2017-10-13 21:36 ` Mathieu Desnoyers
2017-10-16 16:04 ` Carlos O'Donell
2017-10-16 16:04 ` Carlos O'Donell
2017-10-16 16:46 ` Andi Kleen
2017-10-16 16:46 ` Andi Kleen
2017-10-16 22:17 ` Mathieu Desnoyers
2017-10-16 22:17 ` Mathieu Desnoyers
[not found] ` <21865534.42661.1508192263844.JavaMail.zimbra-vg+e7yoeK/dWk0Htik3J/w@public.gmane.org>
2017-10-17 16:19 ` Ben Maurer
2017-10-17 16:19 ` Ben Maurer
[not found] ` <CY4PR15MB168879D6220D976B04FE482CCF4C0-ZVJ2su15u+xeX4ZvlgGe+Yd3EbNNOtPMvxpqHgZTriW3zl9H0oFU5g@public.gmane.org>
2017-10-17 16:33 ` Mathieu Desnoyers
2017-10-17 16:33 ` Mathieu Desnoyers
[not found] ` <1292309161.43101.1508258000235.JavaMail.zimbra-vg+e7yoeK/dWk0Htik3J/w@public.gmane.org>
2017-10-17 16:41 ` Ben Maurer
2017-10-17 16:41 ` Ben Maurer
[not found] ` <CY4PR15MB16886FD43FB48592F3F5892FCF4C0-ZVJ2su15u+xeX4ZvlgGe+Yd3EbNNOtPMvxpqHgZTriW3zl9H0oFU5g@public.gmane.org>
2017-10-17 17:48 ` Mathieu Desnoyers
2017-10-17 17:48 ` Mathieu Desnoyers
2017-10-18 6:22 ` Greg KH
2017-10-18 6:22 ` Greg KH
[not found] ` <20171018062226.GB18857-U8xfFu+wG4EAvxtiuMwx3w@public.gmane.org>
2017-10-18 16:28 ` Mathieu Desnoyers
2017-10-18 16:28 ` Mathieu Desnoyers
2017-10-14 3:01 ` Andi Kleen
2017-10-14 3:01 ` Andi Kleen
2017-10-14 4:05 ` Linus Torvalds
2017-10-14 4:05 ` Linus Torvalds
2017-10-14 11:37 ` Mathieu Desnoyers
2017-10-14 11:37 ` Mathieu Desnoyers
2017-10-13 12:50 ` Florian Weimer
2017-10-13 13:40 ` Mathieu Desnoyers
2017-10-13 13:40 ` Mathieu Desnoyers
2017-10-13 13:56 ` Florian Weimer
2017-10-13 13:56 ` Florian Weimer
2017-10-13 14:27 ` Mathieu Desnoyers
2017-10-13 14:27 ` Mathieu Desnoyers
2017-10-13 17:24 ` Andy Lutomirski
2017-10-13 17:24 ` Andy Lutomirski
[not found] ` <CALCETrXccCp8apoyUJV8kWLOavnFnenZoU-fbb6cOVZvWp-fnA-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2017-10-13 17:53 ` Florian Weimer
2017-10-13 17:53 ` Florian Weimer
[not found] ` <3358e696-43e9-15d3-9634-68e9da79e121-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2017-10-13 18:17 ` Andy Lutomirski
2017-10-13 18:17 ` Andy Lutomirski
[not found] ` <CALCETrVWZxC=mT9p7HTrAwcAdMzaxwa=A-O0uQt79qy1Cpky_g-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2017-10-14 11:53 ` Mathieu Desnoyers
2017-10-14 11:53 ` Mathieu Desnoyers
2017-10-18 16:41 ` Ben Maurer
[not found] ` <CY4PR15MB1688286D6B1283A1C234BAE6CF4E0-ZVJ2su15u+xeX4ZvlgGe+Yd3EbNNOtPMvxpqHgZTriW3zl9H0oFU5g@public.gmane.org>
2017-10-18 18:11 ` Mathieu Desnoyers
2017-10-18 18:11 ` Mathieu Desnoyers
[not found] ` <515879378.43966.1508350299712.JavaMail.zimbra-vg+e7yoeK/dWk0Htik3J/w@public.gmane.org>
2017-10-19 11:35 ` Mathieu Desnoyers
2017-10-19 11:35 ` Mathieu Desnoyers
2017-10-19 17:01 ` Florian Weimer
2017-10-19 17:01 ` Florian Weimer
2017-10-23 17:30 ` Ben Maurer
2017-10-23 17:30 ` Ben Maurer
[not found] ` <CY4PR15MB16888F91F41A4A1D322C102CCF460-ZVJ2su15u+xeX4ZvlgGe+Yd3EbNNOtPMvxpqHgZTriW3zl9H0oFU5g@public.gmane.org>
2017-10-23 20:44 ` Mathieu Desnoyers
2017-10-23 20:44 ` Mathieu Desnoyers
2017-10-12 23:03 ` [RFC PATCH for 4.15 02/14] tracing: instrument restartable sequences Mathieu Desnoyers
2017-10-12 23:03 ` [RFC PATCH for 4.15 03/14] Restartable sequences: ARM 32 architecture support Mathieu Desnoyers
2017-10-12 23:03 ` [RFC PATCH for 4.15 04/14] Restartable sequences: wire up ARM 32 system call Mathieu Desnoyers
2017-10-12 23:03 ` [RFC PATCH for 4.15 05/14] Restartable sequences: x86 32/64 architecture support Mathieu Desnoyers
2017-10-12 23:03 ` [RFC PATCH for 4.15 06/14] Restartable sequences: wire up x86 32/64 system call Mathieu Desnoyers
2017-10-12 23:03 ` [RFC PATCH for 4.15 07/14] Restartable sequences: powerpc architecture support Mathieu Desnoyers
2017-10-12 23:03 ` [RFC PATCH for 4.15 08/14] Restartable sequences: Wire up powerpc system call Mathieu Desnoyers
2017-10-12 23:03 ` [RFC PATCH for 4.15 09/14] Provide cpu_opv " Mathieu Desnoyers
[not found] ` <20171012230326.19984-10-mathieu.desnoyers-vg+e7yoeK/dWk0Htik3J/w@public.gmane.org>
2017-10-13 13:57 ` Alan Cox
2017-10-13 13:57 ` Alan Cox
2017-10-13 14:50 ` Mathieu Desnoyers
2017-10-13 14:50 ` Mathieu Desnoyers
[not found] ` <854849583.40647.1507906233368.JavaMail.zimbra-vg+e7yoeK/dWk0Htik3J/w@public.gmane.org>
2017-10-14 14:22 ` Mathieu Desnoyers
2017-10-14 14:22 ` Mathieu Desnoyers
2017-10-13 17:20 ` Andy Lutomirski
2017-10-13 17:20 ` Andy Lutomirski
2017-10-14 2:50 ` Andi Kleen [this message]
2017-10-14 2:50 ` Andi Kleen
[not found] ` <20171014025029.GL2482-1g7Xle2YJi4/4alezvVtWx2eb7JE58TQ@public.gmane.org>
2017-10-14 13:35 ` Mathieu Desnoyers
2017-10-14 13:35 ` Mathieu Desnoyers
2017-10-12 23:03 ` [RFC PATCH for 4.15 10/14] cpu_opv: Wire up x86 32/64 " Mathieu Desnoyers
2017-10-12 23:03 ` [RFC PATCH for 4.15 11/14] cpu_opv: Wire up powerpc " Mathieu Desnoyers
2017-10-12 23:03 ` [RFC PATCH for 4.15 12/14] cpu_opv: Wire up ARM32 " Mathieu Desnoyers
2017-10-12 23:03 ` [RFC PATCH for 4.15 13/14] cpu_opv: Implement selftests Mathieu Desnoyers
2017-10-12 23:03 ` [RFC PATCH for 4.15 14/14] Restartable sequences: Provide self-tests Mathieu Desnoyers
2017-10-16 2:51 ` Michael Ellerman
2017-10-16 2:51 ` Michael Ellerman
2017-10-16 14:23 ` Mathieu Desnoyers
2017-10-16 14:23 ` Mathieu Desnoyers
[not found] ` <399058130.42156.1508163782335.JavaMail.zimbra-vg+e7yoeK/dWk0Htik3J/w@public.gmane.org>
2017-10-17 10:38 ` Michael Ellerman
2017-10-17 10:38 ` Michael Ellerman
2017-10-17 13:50 ` Mathieu Desnoyers
2017-10-17 13:50 ` Mathieu Desnoyers
[not found] ` <871sm3n6sy.fsf-W0DJWXSxmBNbyGPkN3NxC2scP1bn1w/D@public.gmane.org>
2017-10-16 18:50 ` Mathieu Desnoyers
2017-10-16 18:50 ` Mathieu Desnoyers
[not found] ` <1998166049.42520.1508179805908.JavaMail.zimbra-vg+e7yoeK/dWk0Htik3J/w@public.gmane.org>
2017-10-17 10:36 ` Michael Ellerman
2017-10-17 10:36 ` Michael Ellerman
[not found] ` <87d15mjc1g.fsf-W0DJWXSxmBNbyGPkN3NxC2scP1bn1w/D@public.gmane.org>
2017-10-17 13:50 ` Mathieu Desnoyers
2017-10-17 13:50 ` Mathieu Desnoyers
[not found] ` <1618170495.42951.1508248216596.JavaMail.zimbra-vg+e7yoeK/dWk0Htik3J/w@public.gmane.org>
2017-10-18 5:45 ` Michael Ellerman
2017-10-18 5:45 ` Michael Ellerman
[not found] ` <20171012230326.19984-15-mathieu.desnoyers-vg+e7yoeK/dWk0Htik3J/w@public.gmane.org>
2017-10-16 3:00 ` Michael Ellerman
2017-10-16 3:00 ` Michael Ellerman
2017-10-16 3:48 ` Boqun Feng
2017-10-16 3:48 ` Boqun Feng
2017-10-16 11:48 ` Michael Ellerman
2017-10-16 11:48 ` Michael Ellerman
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=20171014025029.GL2482@two.firstfloor.org \
--to=andi-vw/nlti1exurpaaqcnn02g@public.gmane.org \
--cc=ahh-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org \
--cc=akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org \
--cc=bmaurer-b10kYP2dOMg@public.gmane.org \
--cc=boqun.feng-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org \
--cc=catalin.marinas-5wv7dgnIgG8@public.gmane.org \
--cc=cl-vYTEC60ixJUAvxtiuMwx3w@public.gmane.org \
--cc=davejwatson-b10kYP2dOMg@public.gmane.org \
--cc=hpa-YMNOUZJC4hwAvxtiuMwx3w@public.gmane.org \
--cc=josh-iaAMLnmF4UmaiuxdJuQwMA@public.gmane.org \
--cc=linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org \
--cc=linux-lFZ/pmaqli7XmaaqVzeoHQ@public.gmane.org \
--cc=luto-kltTT9wpgjJwATOyAt5JVQ@public.gmane.org \
--cc=mathieu.desnoyers-vg+e7yoeK/dWk0Htik3J/w@public.gmane.org \
--cc=mingo-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org \
--cc=paulmck-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org \
--cc=peterz-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org \
--cc=pjt-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org \
--cc=rostedt-nx8X9YLhiw1AfugRpC6u6w@public.gmane.org \
--cc=tglx-hfZtesqFncYOwBW4kG4KsQ@public.gmane.org \
--cc=torvalds-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org \
--cc=will.deacon-5wv7dgnIgG8@public.gmane.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.