From owner-freebsd-fs@freebsd.org  Fri Jan  8 10:17:32 2016
Return-Path: <owner-freebsd-fs@freebsd.org>
Delivered-To: freebsd-fs@mailman.ysv.freebsd.org
Received: from mx1.freebsd.org (mx1.freebsd.org
 [IPv6:2001:1900:2254:206a::19:1])
 by mailman.ysv.freebsd.org (Postfix) with ESMTP id C4886A675FD
 for <freebsd-fs@mailman.ysv.freebsd.org>; Fri,  8 Jan 2016 10:17:32 +0000 (UTC)
 (envelope-from jdarcy@redhat.com)
Received: from mx4-phx2.redhat.com (mx4-phx2.redhat.com [209.132.183.25])
 (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits))
 (Client CN "mx1.redhat.com",
 Issuer "DigiCert SHA2 Extended Validation Server CA" (verified OK))
 by mx1.freebsd.org (Postfix) with ESMTPS id A78A51FE0
 for <freebsd-fs@freebsd.org>; Fri,  8 Jan 2016 10:17:32 +0000 (UTC)
 (envelope-from jdarcy@redhat.com)
Received: from zmail12.collab.prod.int.phx2.redhat.com
 (zmail12.collab.prod.int.phx2.redhat.com [10.5.83.14])
 by mx4-phx2.redhat.com (8.13.8/8.13.8) with ESMTP id u08AHU5O024635;
 Fri, 8 Jan 2016 05:17:30 -0500
Date: Fri, 8 Jan 2016 05:17:30 -0500 (EST)
From: Jeff Darcy <jdarcy@redhat.com>
To: Raghavendra G <raghavendra@gluster.com>
Cc: Xavier Hernandez <xhernandez@datalab.es>,
 freebsd-fs <freebsd-fs@freebsd.org>,
 Gluster Devel <gluster-devel@gluster.org>,
 Hubbard Jordan <jkh@ixsystems.com>
Message-ID: <1924941590.6473225.1452248249994.JavaMail.zimbra@redhat.com>
In-Reply-To: <CADRNtgRM17Eg3Z=LWifVNo=ai72dMiEVRKS3RwNfQ-dK7Pspew@mail.gmail.com>
References: <571237035.145690509.1451437960464.JavaMail.zimbra@uoguelph.ca>
 <20151230103152.GS13942@ndevos-x240.usersys.redhat.com>
 <2D8C2729-D556-479B-B4E2-66E1BB222F41@ixsystems.com>
 <1083933309.146084334.1451517977647.JavaMail.zimbra@uoguelph.ca>
 <CADRNtgStOg8UZfxNt-SzvvPf7d1J7CC_gi49ww3BbixU0Ey-rg@mail.gmail.com>
 <568F6D07.6070500@datalab.es>
 <CADRNtgRM17Eg3Z=LWifVNo=ai72dMiEVRKS3RwNfQ-dK7Pspew@mail.gmail.com>
Subject: Re: [Gluster-devel] FreeBSD port of GlusterFS racks up a lot of CPU
 usage
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: 7bit
X-Originating-IP: [10.3.113.99]
X-Mailer: Zimbra 8.0.6_GA_5922 (ZimbraWebClient - GC47
 ([unknown])/8.0.6_GA_5922)
Thread-Topic: FreeBSD port of GlusterFS racks up a lot of CPU usage
Thread-Index: nzgvBLPPgcBXuRsf6GlZU17foVfxCA==
X-BeenThere: freebsd-fs@freebsd.org
X-Mailman-Version: 2.1.20
Precedence: list
List-Id: Filesystems <freebsd-fs.freebsd.org>
List-Unsubscribe: <https://lists.freebsd.org/mailman/options/freebsd-fs>,
 <mailto:freebsd-fs-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/freebsd-fs/>
List-Post: <mailto:freebsd-fs@freebsd.org>
List-Help: <mailto:freebsd-fs-request@freebsd.org?subject=help>
List-Subscribe: <https://lists.freebsd.org/mailman/listinfo/freebsd-fs>,
 <mailto:freebsd-fs-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Fri, 08 Jan 2016 10:17:32 -0000

> > I don't know anything about gluster's poll implementation so I may
> > be totally wrong, but would it be possible to use an eventfd (or a
> > pipe if eventfd is not supported) to signal the need to add more
> > file descriptors to the poll call ?
> >
> >
> > The poll call should listen on this new fd. When we need to change
> > the fd list, we should simply write to the eventfd or pipe from
> > another thread.  This will cause the poll call to return and we will
> > be able to change the fd list without having a short timeout nor
> > having to decide on any trade-off.
> 
>
> Thats a nice idea. Based on my understanding of why timeouts are being
> used, this approach can work.

The own-thread code which preceded the current poll implementation did
something similar, using a pipe fd to be woken up for new *outgoing*
messages.  That code still exists, and might provide some insight into
how to do this for the current poll code.