From owner-freebsd-net@FreeBSD.ORG Wed Oct 20 21:05:18 2004 Return-Path: Delivered-To: freebsd-net@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 9B48216A4CE for ; Wed, 20 Oct 2004 21:05:18 +0000 (GMT) Received: from maxwell.syr.edu (maxwell.syr.edu [128.230.129.5]) by mx1.FreeBSD.org (Postfix) with ESMTP id 2D11043D46 for ; Wed, 20 Oct 2004 21:05:18 +0000 (GMT) (envelope-from cmsedore@maxwell.syr.edu) Received: from exchange.maxwell.syr.edu (excluster2.maxwell.syr.edu [128.230.129.231]) by maxwell.syr.edu (8.12.10/8.9.1) with ESMTP id i9KL5FBf031304; Wed, 20 Oct 2004 17:05:16 -0400 (EDT) X-MimeOLE: Produced By Microsoft Exchange V6.5.6944.0 Content-class: urn:content-classes:message MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable Date: Wed, 20 Oct 2004 17:05:17 -0400 Message-ID: <32A8B2CB12BFC84D8D11D872C787AA9A058EE914@EXCHANGE.forest.maxwell.syr.edu> X-MS-Has-Attach: X-MS-TNEF-Correlator: Thread-Topic: aio_connect ? Thread-Index: AcS242d2QiwOIewWTamIn1cEu7/kXQAA+woQ From: "Christopher M. Sedore" To: "Igor Sysoev" cc: freebsd-net@freebsd.org cc: "Ronald F. Guilmette" Subject: RE: aio_connect ? X-BeenThere: freebsd-net@freebsd.org X-Mailman-Version: 2.1.1 Precedence: list List-Id: Networking and TCP/IP with FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 20 Oct 2004 21:05:18 -0000 =20 > From: Igor Sysoev [mailto:is@rambler-co.ru]=20 > Subject: RE: aio_connect ? >=20 > On Wed, 20 Oct 2004, Christopher M. Sedore wrote: >=20 > > > While the developing my server nginx, I found the POSIX aio_* > > > operations > > > uncomfortable. I do not mean a different programming style, I mean > > > the aio_read() and aio_write() drawbacks - they have no=20 > scatter-gather > > > capabilities (aio_readv/aio_writev) and they require too many > > > syscalls. > > > E.g, the reading requires > > > *) 3 syscalls for ready data: aio_read(), aio_error(),=20 > aio_return() > > > *) 5 syscalls for non-ready data: aio_read(), aio_error(), > > > waiting for notification, then aio_error(), aio_return(), > > > or if timeout occuired - aio_cancel(), aio_error(). > > > > This is why I added aio_waitcomplete(). It reduces both=20 > cases to two > > syscalls. >=20 > As I understand aio_waitcomplete() returns aiocb of any complete AIO > operation but I need to know the state of the exact AIO,=20 > namely the last > aio_read(). Correct, it won't poll, but what state can you get from calling aio_error() that you don't already know from aio_waitcomplete(). The operation has either completed (successfully or unsuccessfully) or it hasn't. If it hasn't you haven't "gotten it back" via aio_waitcomplete, and if it has, you did. I may be missing something, but how does aio_error() tell you something that you don't already know? > I use kqueue to get AIO notifications. If AIO operation would fail > at the start, will kqueue return notificaiton about this operation ? I don't think so--IIRC, if you have a parameter problem or the operation can't be queued, you'll get an error return from aio_read and no kqueue result. If it is queued, you'll get a kqueue notification. -Chris