From mboxrd@z Thu Jan 1 00:00:00 1970 From: Michael Tokarev Subject: Re: linux-aio usable? Date: Tue, 09 Mar 2010 12:19:11 +0300 Message-ID: <4B96128F.10608@msgid.tls.msk.ru> References: <4B94BF05.20609@redhat.com> <4B9559DA.8000407@msgid.tls.msk.ru> <4B955BD7.1010508@msgid.tls.msk.ru> <4B961003.9010807@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: Bernhard Schmidt , kvm@vger.kernel.org To: Avi Kivity Return-path: Received: from isrv.corpit.ru ([81.13.33.159]:44402 "EHLO isrv.corpit.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753592Ab0CIJTN (ORCPT ); Tue, 9 Mar 2010 04:19:13 -0500 In-Reply-To: <4B961003.9010807@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: Avi Kivity wrote: > On 03/08/2010 10:19 PM, Michael Tokarev wrote: >> Michael Tokarev wrote: >> [] >> >>> Apparently that does not quite work. I just re-compiled kvm with >>> --enable-linux-aio (actually I just installed libaio-dev on debian >>> and qemu-kvm's configure picked it up automatically), and tried >>> a guest. But any I/O fails. >>> >> It has nothing to do with kvm. It is compat_ioctl32 in the kernel >> wrt aio calls. Historically I've a 64bit kernel with 32bit userland, >> and tried 32bit kvm too, and that does not work. But 64bit kvm works >> just fine with aio, and the performance numbers are indeed better. > > Can you elaborate? This sounds like a bug that wants to be fixed. http://thread.gmane.org/gmane.linux.kernel.aio.general/2891 It's missing compat_ioctl for some of the aio opcodes, namely it's PREADV and PWRITE - the only ones used by kvm and the only ones missing in kernel. As far as i can see, current code converts the iocb array just fine, but does not touch iovec array used with p{read,write}v. /mjt