From: "H. Peter Anvin" <hpa@zytor.com>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Denys Vlasenko <dvlasenk@redhat.com>,
Ingo Molnar <mingo@kernel.org>,
Steven Rostedt <rostedt@goodmis.org>,
Borislav Petkov <bp@alien8.de>,
Andy Lutomirski <luto@amacapital.net>,
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>,
the arch/x86 maintainers <x86@kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] x86/asm/entry/64: pack interrupt dispatch table tighter
Date: Fri, 03 Apr 2015 12:06:38 -0700 [thread overview]
Message-ID: <551EE4BE.9090507@zytor.com> (raw)
In-Reply-To: <CA+55aFwQV5Qb1V++wJQXDfv92mGfuwCidO9Y2rRP1ezZG9v4jA@mail.gmail.com>
On 04/03/2015 11:37 AM, Linus Torvalds wrote:
> On Fri, Apr 3, 2015 at 11:35 AM, H. Peter Anvin <hpa@zytor.com> wrote:
>>
>> For the record, I actually measured the impact of the jump-to-jump when
>> I wrote it. It has a small, *but measurable*, positive impact.
>
> What did you compare against, and how did you measure that? I don't
> see how it could *possibly* be faster than just a simple aligned "push
> + jmp".
>
I wish I remembered the exact details; it took a fair bit of gathering
numbers as the spread was quite a bit wider than the delta, but in the
end there were two distribution peaks clearly offset.
I seem to remember it involving a loop running RDTSC continuously and
another RDTSC in the interrupt path.
-hpa
next prev parent reply other threads:[~2015-04-03 19:07 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-04-03 11:13 [PATCH] x86/asm/entry/64: pack interrupt dispatch table tighter Denys Vlasenko
2015-04-03 14:03 ` Ingo Molnar
2015-04-03 16:12 ` Denys Vlasenko
2015-04-03 16:54 ` Denys Vlasenko
2015-04-03 18:08 ` Linus Torvalds
2015-04-03 18:35 ` H. Peter Anvin
2015-04-03 18:37 ` Linus Torvalds
2015-04-03 19:06 ` H. Peter Anvin [this message]
2015-04-04 6:42 ` Ingo Molnar
2015-04-03 18:36 ` Denys Vlasenko
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