linux-kernel.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Ingo Molnar <mingo@kernel.org>
To: Andy Lutomirski <luto@amacapital.net>
Cc: Denys Vlasenko <dvlasenk@redhat.com>,
	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 v4 RESEND] x86/asm/entry/32, selftests: Add 'test_syscall_vdso' test
Date: Mon, 14 Sep 2015 10:26:01 +0200	[thread overview]
Message-ID: <20150914082601.GB9274@gmail.com> (raw)
In-Reply-To: <CALCETrWUGuWUPLHy2UwJHfX=c1fDwpL9hk1NwO8fkkHh8gUpnA@mail.gmail.com>


* Andy Lutomirski <luto@amacapital.net> wrote:

> > (I'm not very comfortable about additional six push/pops
> > which are necessary for this to happen. I'm surprised
> > maintainers tentatively agreed to that -
> > I was grilled and asked to prove with measurements
> > that *one* additional push+pop wasn't adding significant overhead).
> 
> I suspect that I need to make the series faster.
> 
> Also, int $0x80 isn't a fast path for any legitimate use case except
> Debian, and I would argue that Debian is just buggy.

So buggy in the sense of not making use of faster syscalls, right? It won't break 
in any visible way, correct?

So if this heavy int80 syscall use happens even with the latest version of Debian 
as well then it would be nice to figure out what's wrong there, and provide an 
optimization patch to their libc guys or so - to make sure we fully understand the 
problem.

Thanks,

	Ingo

  reply	other threads:[~2015-09-14  8:26 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-09-07 15:56 [PATCH v4 RESEND] x86/asm/entry/32, selftests: Add 'test_syscall_vdso' test Denys Vlasenko
2015-09-09 22:01 ` Andy Lutomirski
2015-09-10 19:04   ` Denys Vlasenko
2015-09-10 19:17     ` Andy Lutomirski
2015-09-14  8:26       ` Ingo Molnar [this message]
2015-09-14 17:54         ` Andy Lutomirski
2015-09-14  8:15     ` Ingo Molnar
2015-09-14 17:55       ` Andy Lutomirski
2015-09-15  5:59         ` Ingo Molnar
2015-09-15 18:14           ` Andy Lutomirski
2015-09-16  9:51             ` Ingo Molnar
2015-09-15  6:05 ` Ingo Molnar

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=20150914082601.GB9274@gmail.com \
    --to=mingo@kernel.org \
    --cc=ast@plumgrid.com \
    --cc=bp@alien8.de \
    --cc=dvlasenk@redhat.com \
    --cc=fweisbec@gmail.com \
    --cc=hpa@zytor.com \
    --cc=keescook@chromium.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=luto@amacapital.net \
    --cc=oleg@redhat.com \
    --cc=rostedt@goodmis.org \
    --cc=torvalds@linux-foundation.org \
    --cc=wad@chromium.org \
    --cc=x86@kernel.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).