From: "H. Peter Anvin" <hpa@zytor.com>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <bitbucket@online.de>,
Andi Kleen <andi@firstfloor.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
the arch/x86 maintainers <x86@kernel.org>,
Ingo Molnar <mingo@kernel.org>
Subject: Re: Re-tune x86 uaccess code for PREEMPT_VOLUNTARY
Date: Sat, 10 Aug 2013 16:00:51 -0700 [thread overview]
Message-ID: <5206C623.4020605@zytor.com> (raw)
In-Reply-To: <CA+55aFzhv1v9KatxQ3GUGBZf+zTb_hdx2fJZKT+m5tEcAkWsSQ@mail.gmail.com>
On 08/10/2013 11:51 AM, Linus Torvalds wrote:
> Note that you still want the *test* to be done in C code, because together
> with "unlikely()" you'd likely do pretty close to optimal code
> generation, and hiding the decrement and test and conditional jump in
> asm you wouldn't get the proper instruction scheduling and branch
> following that gcc does.
How much instruction scheduling can gcc actually do given that there is
a barrier involved? I guess some on the RISC architectures which need
load/subtract/store...
-hpa
next prev parent reply other threads:[~2013-08-10 23:01 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-08-09 23:04 Andi Kleen
2013-08-09 23:04 ` [PATCH 01/13] x86: Add 1/2/4/8 byte optimization to 64bit __copy_{from,to}_user_inatomic Andi Kleen
2013-08-09 23:04 ` [PATCH 02/13] x86: Include linux/sched.h in asm/uaccess.h Andi Kleen
2013-08-09 23:04 ` [PATCH 03/13] tree-sweep: Include linux/sched.h for might_sleep users Andi Kleen
2013-08-09 23:04 ` [PATCH 04/13] Move might_sleep and friends from kernel.h to sched.h Andi Kleen
2013-08-09 23:04 ` [PATCH 05/13] sched: mark should_resched() __always_inline Andi Kleen
2013-08-09 23:04 ` [PATCH 06/13] x86: Add 32bit versions of SAVE_ALL/RESTORE_ALL to calling.h Andi Kleen
2013-08-09 23:04 ` [PATCH 07/13] Add might_fault_debug_only() Andi Kleen
2013-08-14 18:24 ` Michael S. Tsirkin
2013-08-09 23:04 ` [PATCH 08/13] x86: Move cond_resched into the out of line put_user code Andi Kleen
2013-08-09 23:04 ` [PATCH 09/13] x86: Move cond_resched into the out of line get_user code Andi Kleen
2013-08-09 23:04 ` [PATCH 10/13] x86: Move cond resched for copy_{from,to}_user into low level code 64bit Andi Kleen
2013-08-10 15:42 ` Linus Torvalds
2013-08-10 16:10 ` Andi Kleen
2013-08-10 16:27 ` Linus Torvalds
2013-08-10 18:23 ` Borislav Petkov
2013-08-10 19:05 ` Jörn Engel
2013-08-20 21:03 ` KOSAKI Motohiro
2013-08-15 5:04 ` Michael S. Tsirkin
2013-08-09 23:04 ` [PATCH 11/13] sched: Inline the need_resched test into the caller for _cond_resched Andi Kleen
2013-08-09 23:04 ` [PATCH 12/13] x86: move __copy_*_nocache might fault check out of line Andi Kleen
2013-08-09 23:04 ` [PATCH 13/13] x86: drop cond rescheds from __copy_{from,to}_user Andi Kleen
2013-08-10 4:42 ` Re-tune x86 uaccess code for PREEMPT_VOLUNTARY H. Peter Anvin
2013-08-10 5:55 ` Mike Galbraith
2013-08-10 16:09 ` H. Peter Anvin
2013-08-10 16:43 ` Linus Torvalds
2013-08-10 17:18 ` H. Peter Anvin
2013-08-10 18:51 ` Linus Torvalds
2013-08-10 19:18 ` H. Peter Anvin
2013-08-10 20:26 ` H. Peter Anvin
2013-08-10 23:00 ` H. Peter Anvin [this message]
2013-08-11 4:17 ` Mike Galbraith
2013-08-11 4:27 ` H. Peter Anvin
2013-08-11 4:36 ` Mike Galbraith
2013-08-11 4:57 ` H. Peter Anvin
2013-08-11 5:58 ` Mike Galbraith
2013-08-13 18:09 ` H. Peter Anvin
2013-08-13 18:12 ` Andi Kleen
2013-08-14 18:27 ` Michael S. Tsirkin
2013-08-14 22:08 ` Andi Kleen
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