[libvirt] [PATCH 0/8] Avoid filesystem cache pollution during virsh save

Saving a domain's state creates a large file, which risks polluting the filesystem cache and slowing down a system. If a system has a lot of domians simultaneously being saved (such as the libvirt-guests init script doing managed saves), then this can cause noticeable slowdown due to filesystem thrashing. This patch series has been successfully tested to do 'virsh save dom file --direct', with lsof(1) used to verify that O_DIRECT was in use, and the resulting file was successfully used with 'virsh restore file'. Still to come - wire up O_DIRECT on the 'virsh restore' path (yes, that means adding virDomainRestoreFlags - if only we had had the foresight to use flags everywhere). Wire up qemu.conf to allow the automatic use of --direct on automatic core dumps. Wire up libvirt-guests init script to allow the use of --direct. But I had enough in place to get the review started now. Also, this series demonstrates some of the points I was making about adding a new Flags API in this thread: https://www.redhat.com/archives/libvir-list/2011-July/msg00762.html This series requires and was tested on top of these (un-acked) patches: https://www.redhat.com/archives/libvir-list/2011-July/msg00670.html https://www.redhat.com/archives/libvir-list/2011-July/msg00675.html Eric Blake (8): save: document new public API save: wire up remote protocol save: wire up trivial saveFlags implementations save: add --direct flag to virsh save operations save: let iohelper handle inherited fd save: let iohelper work on O_DIRECT fds save: add virDirectFd wrapper type save: support O_DIRECT during qemu saves cfg.mk | 1 + configure.ac | 6 +- include/libvirt/libvirt.h.in | 14 +++ po/POTFILES.in | 1 + src/Makefile.am | 1 + src/driver.h | 6 ++ src/fdstream.c | 32 +++----- src/libvirt.c | 94 +++++++++++++++++++++- src/libvirt_private.syms | 6 ++ src/libvirt_public.syms | 5 + src/libxl/libxl_driver.c | 17 ++++- src/qemu/qemu_driver.c | 76 +++++++++++++----- src/remote/remote_driver.c | 1 + src/remote/remote_protocol.x | 11 +++- src/remote_protocol-structs | 6 ++ src/test/test_driver.c | 20 ++++- src/util/iohelper.c | 185 +++++++++++++++++++++++++++++++---------- src/util/virdirect.c | 149 +++++++++++++++++++++++++++++++++ src/util/virdirect.h | 37 +++++++++ src/vbox/vbox_tmpl.c | 19 ++++- src/xen/xen_driver.c | 17 ++++- tools/virsh.c | 12 +++- tools/virsh.pod | 17 +++- 23 files changed, 632 insertions(+), 101 deletions(-) create mode 100644 src/util/virdirect.c create mode 100644 src/util/virdirect.h -- 1.7.4.4