linux-kernel - Re: [PATCH RFC 5/6] epoll: Add implementation for epoll_mod

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20150123062050.GA7071@ad.nay.redhat.com>
Date:	Fri, 23 Jan 2015 14:20:50 +0800
From:	Fam Zheng <famz@...hat.com>
To:	Andy Lutomirski <luto@...capital.net>
Cc:	Paolo Bonzini <pbonzini@...hat.com>,
	"Michael Kerrisk (man-pages)" <mtk.manpages@...il.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, X86 ML <x86@...nel.org>,
	Alexander Viro <viro@...iv.linux.org.uk>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Kees Cook <keescook@...omium.org>,
	David Herrmann <dh.herrmann@...il.com>,
	Alexei Starovoitov <ast@...mgrid.com>,
	Miklos Szeredi <mszeredi@...e.cz>,
	David Drysdale <drysdale@...gle.com>,
	Oleg Nesterov <oleg@...hat.com>,
	"David S. Miller" <davem@...emloft.net>,
	Vivek Goyal <vgoyal@...hat.com>,
	Mike Frysinger <vapier@...too.org>,
	"Theodore Ts'o" <tytso@....edu>,
	Heiko Carstens <heiko.carstens@...ibm.com>,
	Rasmus Villemoes <linux@...musvillemoes.dk>,
	Rashika Kheria <rashika.kheria@...il.com>,
	Hugh Dickins <hughd@...gle.com>,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Linux FS Devel <linux-fsdevel@...r.kernel.org>,
	Linux API <linux-api@...r.kernel.org>,
	Josh Triplett <josh@...htriplett.org>
Subject: Re: [PATCH RFC 5/6] epoll: Add implementation for epoll_mod_wait

On Thu, 01/22 13:12, Andy Lutomirski wrote:
> On Wed, Jan 21, 2015 at 3:50 AM, Paolo Bonzini <pbonzini@...hat.com> wrote:
> >
> >
> > On 21/01/2015 12:14, Fam Zheng wrote:
> >> > My take for simplicity will be leaving epoll_ctl as-is, and my take for
> >> > performance will be epoll_pwait1. And I don't really like putting my time on
> >> > epoll_ctl_batch, thinking it as a ambivalent compromise in between.
> >>
> >> > I agree with Michael actually.  The big change is going from O(n)
> >> > epoll_ctl calls to O(1), and epoll_ctl_batch achieves that just fine.
> >> > Changing 2 syscalls to 1 is the icing on the cake, but we're talking of
> >> > a fraction of a microsecond.
> >>
> >> Maybe I'm missing something, but in common cases, the set of fds for epoll_wait
> >> doesn't change that radically from one iteration to another, does it?
> >
> > That depends on the application.
> 
> In my application, the set of fds almost never changes, but the set of
> events I want changes all the time.  The main thing that changes is
> whether I care about EPOLLOUT.  If I'm ready to send something, then I
> want EPOLLOUT.  If I'm not ready, then I don't want EPOLLOUT.
> 

OK, I'll split it to epoll_ctl_batch and epoll_pwait1 as Micheal suggested in
v2.

Fam
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/