From: Denys Vlasenko <dvlasenk@redhat.com>
To: Josh Triplett <josh@joshtriplett.org>,
Andy Lutomirski <luto@amacapital.net>
Cc: Ingo Molnar <mingo@kernel.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
Steven Rostedt <rostedt@goodmis.org>,
Borislav Petkov <bp@alien8.de>, "H. Peter Anvin" <hpa@zytor.com>,
Oleg Nesterov <oleg@redhat.com>,
Frederic Weisbecker <fweisbec@gmail.com>,
Alexei Starovoitov <ast@plumgrid.com>,
Will Drewry <wad@chromium.org>, Kees Cook <keescook@chromium.org>,
X86 ML <x86@kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 2/2] x86/asm/entry/32: Remove unnecessary optimization in stub32_clone
Date: Wed, 22 Apr 2015 20:04:34 +0200 [thread overview]
Message-ID: <5537E2B2.5050006@redhat.com> (raw)
In-Reply-To: <20150422171005.GA1020@jtriplet-mobl1>
On 04/22/2015 07:10 PM, Josh Triplett wrote:
> On Wed, Apr 22, 2015 at 09:54:24AM -0700, Andy Lutomirski wrote:
>> On Wed, Apr 22, 2015 at 9:40 AM, Denys Vlasenko <dvlasenk@redhat.com> wrote:
>>> Really swap arguments #4 and #5 in stub32_clone instead of "optimizing"
>>> it into a move.
>>>
>>> Yes, tls_val is currently unused. Yes, on some CPUs XCHG is a little bit
>>> more expensive than MOV. But a cycle or two on an expensive syscall like
>>> clone() is way below noise floor, and obfuscation of logic introduced
>>> by this optimization is simply not worth it.
>>
>> Ditto re: Josh's patch.
>
> I do think my two-patch HAVE_COPY_THREAD_TLS series should go in fixing
> this, but I'd like to see the final version of Denys' comment added on
> top of it (with an update to the type and name of the tls argument to
> match the changes to sys_clone).
>
> Denys, would you consider submitting a patch adding your comment on top
> of the two-patch series I just sent?
Okay.
next prev parent reply other threads:[~2015-04-22 18:05 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-04-22 16:40 [PATCH 1/2] x86/asm/entry/32: Explain stub32_clone logic Denys Vlasenko
2015-04-22 16:40 ` [PATCH 2/2] x86/asm/entry/32: Remove unnecessary optimization in stub32_clone Denys Vlasenko
2015-04-22 16:54 ` Andy Lutomirski
2015-04-22 17:10 ` Josh Triplett
2015-04-22 18:04 ` Denys Vlasenko [this message]
2015-04-22 18:22 ` Linus Torvalds
2015-04-22 20:12 ` Josh Triplett
2015-04-23 6:24 ` Ingo Molnar
2015-04-23 7:36 ` Josh Triplett
2015-04-22 16:53 ` [PATCH 1/2] x86/asm/entry/32: Explain stub32_clone logic Andy Lutomirski
2015-06-03 13:58 Denys Vlasenko
2015-06-03 13:58 ` [PATCH 2/2] x86/asm/entry/32: Remove unnecessary optimization in stub32_clone Denys Vlasenko
2015-06-03 16:38 ` Josh Triplett
2015-06-04 10:07 ` Denys Vlasenko
2015-06-04 15:58 ` Josh Triplett
2015-06-05 11:44 ` Ingo Molnar
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