From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ulrich Drepper Subject: Re: [RFC 1/4] kevent: core files. Date: Tue, 01 Aug 2006 00:53:10 -0700 Message-ID: <44CF0866.3000505@redhat.com> References: <20060731103322.GA1898@2ka.mipt.ru> <20060731105037.GA2073@2ka.mipt.ru> <20060731.035716.39159213.davem@davemloft.net> <20060731105943.GA26114@gondor.apana.org.au> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="------------enig1E9F03E3BCAB44146EFEB583" Cc: David Miller , johnpol@2ka.mipt.ru, zach.brown@oracle.com, linux-kernel@vger.kernel.org, netdev@vger.kernel.org Return-path: Received: from mx1.redhat.com ([66.187.233.31]:16306 "EHLO mx1.redhat.com") by vger.kernel.org with ESMTP id S1161350AbWHAHvz (ORCPT ); Tue, 1 Aug 2006 03:51:55 -0400 To: Herbert Xu In-Reply-To: <20060731105943.GA26114@gondor.apana.org.au> Sender: netdev-owner@vger.kernel.org List-Id: netdev.vger.kernel.org This is an OpenPGP/MIME signed message (RFC 2440 and 3156) --------------enig1E9F03E3BCAB44146EFEB583 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Herbert Xu wrote: > The other to consider is that events don't come from the hardware. > Events are written by the kernel. So if user-space is just reading > the events that we've written, then there are no cache misses at all. Not quite true. The ring buffer can be written to from another processor. The kernel thread responsible for generating the event (receiving data from network or disk, expired timer) can run independently on another CPU. This is the case to keep in mind here. I thought Zach and the other involved in the discussions in Ottawa said this has been shown to be a problem and that a ring buffer implementation with something other than simple front and back pointers is preferable. --=20 =E2=9E=A7 Ulrich Drepper =E2=9E=A7 Red Hat, Inc. =E2=9E=A7 444 Castro St = =E2=9E=A7 Mountain View, CA =E2=9D=96 --------------enig1E9F03E3BCAB44146EFEB583 Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.4 (GNU/Linux) Comment: Using GnuPG with Fedora - http://enigmail.mozdev.org iD8DBQFEzwhm2ijCOnn/RHQRAufPAKCmVw/xv8k+jz0pt/e9r+JQdUUYhACffjtj WlYBRLKz2lSQK7z5fLWyQqQ= =zcGF -----END PGP SIGNATURE----- --------------enig1E9F03E3BCAB44146EFEB583--