Hi ! Correct me if I''m wrong, but considering this : - FC6 ships with Xen 3.0.3 with xen-kernel version 2.6.20 - Xen 3.0.3 has a serious performance bug (see http://lists.xensource.com/archives/html/xen-devel/2006-10/msg00487.html ) - This bug is fixed in Xen 3.0.4 - Xen 3.0.4 ships with xen-kernel 2.6.16 Is it possible to install both a recent kernel version (>2.6.18) AND Xen 3.0.4 and still take advantage of the FC6 update mechanism ? Can I install the xen kernel shipped with FC6 and regularely updated through the update system, AND have a manual installation of Xen 3.0.4 ?? Luc
On Wed, Apr 25, 2007 at 03:31:49PM -0400, Boudreau Luc wrote:> Correct me if I''m wrong, but considering this : > > - FC6 ships with Xen 3.0.3 with xen-kernel version 2.6.20 > > - Xen 3.0.3 has a serious performance bug (see > http://lists.xensource.com/archives/html/xen-devel/2006-10/msg00487.html > ) > > - This bug is fixed in Xen 3.0.4No it isn''t. The performance bug is actually at least x2 worse in Xen 3.0.4 http://lists.xensource.com/archives/html/xen-devel/2007-04/msg00663.html If you want immediate relief from xenstore performance problems in 3.0.3, the quick *hack* is to add this in /etc/init.d/xend if [ -d /dev/shm ]; then if [ ! -d /dev/shm/xenstored ]; then mkdir /dev/shm/xenstored chcon system_u:object_r:xenstored_var_lib_t /dev/shm/xenstored/ mount --bind /dev/shm/xenstored /var/lib/xenstored fi fi Immediately after the ''modprobe netloop'' line in the start() function. This stops xenstored I/O hitting your disk, by moving it into a ramdisk. There''s no need to keep xenstored state around between reboots so this is a reasonably safe hack. I''m experimenting with more long term fixes. Dan. -- |=- Red Hat, Engineering, Emerging Technologies, Boston. +1 978 392 2496 -=| |=- Perl modules: http://search.cpan.org/~danberr/ -=| |=- Projects: http://freshmeat.net/~danielpb/ -=| |=- GnuPG: 7D3B9505 F3C9 553F A1DA 4AC2 5648 23C1 B3DF F742 7D3B 9505 -=|
Wow, thanks for the quick answer AND the solution. Frankly, I''m impressed. Nothing to report on this hack then ? No side effects ? (except the fact that the state is not persisted, which is irrelevent anyways...) Luc -----Message d''origine----- De : Daniel P. Berrange [mailto:berrange@redhat.com] Envoyé : 25 avril 2007 15:38 À : Boudreau Luc Cc : fedora-xen@redhat.com Objet : Re: [Fedora-xen] Xen 3.0.4... On Wed, Apr 25, 2007 at 03:31:49PM -0400, Boudreau Luc wrote:> Correct me if I''m wrong, but considering this : > > - FC6 ships with Xen 3.0.3 with xen-kernel version 2.6.20 > > - Xen 3.0.3 has a serious performance bug (see > http://lists.xensource.com/archives/html/xen-devel/2006-10/msg00487.html > ) > > - This bug is fixed in Xen 3.0.4No it isn''t. The performance bug is actually at least x2 worse in Xen 3.0.4 http://lists.xensource.com/archives/html/xen-devel/2007-04/msg00663.html If you want immediate relief from xenstore performance problems in 3.0.3, the quick *hack* is to add this in /etc/init.d/xend if [ -d /dev/shm ]; then if [ ! -d /dev/shm/xenstored ]; then mkdir /dev/shm/xenstored chcon system_u:object_r:xenstored_var_lib_t /dev/shm/xenstored/ mount --bind /dev/shm/xenstored /var/lib/xenstored fi fi Immediately after the ''modprobe netloop'' line in the start() function. This stops xenstored I/O hitting your disk, by moving it into a ramdisk. There''s no need to keep xenstored state around between reboots so this is a reasonably safe hack. I''m experimenting with more long term fixes. Dan. -- |=- Red Hat, Engineering, Emerging Technologies, Boston. +1 978 392 2496 -=| |=- Perl modules: http://search.cpan.org/~danberr/ -=| |=- Projects: http://freshmeat.net/~danielpb/ -=| |=- GnuPG: 7D3B9505 F3C9 553F A1DA 4AC2 5648 23C1 B3DF F742 7D3B 9505 -=|
On Wed, Apr 25, 2007 at 03:42:22PM -0400, Boudreau Luc wrote:> > Wow, thanks for the quick answer AND the solution. Frankly, I''m > impressed. > > Nothing to report on this hack then ? No side effects ? (except > the fact that the state is not persisted, which is irrelevent anyways...)The hack isn''t a complete solution - it merely lowers the performance hit to some degree by removing disk I/O. There is still considerable CPU usage in xenstored simply by copying data to/from tmpfs RAM disk. In my tests using tmpfs reduces CPU usage from 60% to 30%. The real fix in XenD ought to reduce xenstored CPU usage to < 1 % Dan. -- |=- Red Hat, Engineering, Emerging Technologies, Boston. +1 978 392 2496 -=| |=- Perl modules: http://search.cpan.org/~danberr/ -=| |=- Projects: http://freshmeat.net/~danielpb/ -=| |=- GnuPG: 7D3B9505 F3C9 553F A1DA 4AC2 5648 23C1 B3DF F742 7D3B 9505 -=|