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Libvirt provides a portable, long term stable C API for managing the
virtualization technologies provided by many operating systems. It
includes support for QEMU, KVM, Xen, LXC, bhyve, Virtuozzo, VMware
vCenter and ESX, VMware Desktop, Hyper-V, VirtualBox and the POWER
Hypervisor.
d685c0f91b
Recent testing on large memory systems revealed a bug in the Xen xl tool's freemem() function. When autoballooning is enabled, freemem() is used to ensure enough memory is available to start a domain, ballooning dom0 if necessary. When ballooning large amounts of memory from dom0, freemem() would exceed its self-imposed wait time and return an error. Meanwhile, dom0 continued to balloon. Starting the domain later, after sufficient memory was ballooned from dom0, would succeed. The libvirt implementation in libxlDomainFreeMem() suffers the same bug since it is modeled after freemem(). In the end, the best place to fix the bug on the Xen side was to slightly change the behavior of libxl_wait_for_memory_target(). Instead of failing after caller-provided wait_sec, the function now blocks as long as dom0 memory ballooning is progressing. It will return failure only when more memory is needed to reach the target and wait_sec have expired with no progress being made. See xen.git commit fd3aa246. There was a dicussion on how this would affect other libxl apps like libvirt http://lists.xen.org/archives/html/xen-devel/2015-03/msg00739.html If libvirt containing this patch was build against a Xen containing the old libxl_wait_for_memory_target() behavior, libxlDomainFreeMem() will fail after 30 sec and domain creation will be terminated. Without this patch and with old libxl_wait_for_memory_target() behavior, libxlDomainFreeMem() does not succeed after 30 sec, but returns success anyway. Domain creation continues resulting in all sorts of fun stuff like cpu soft lockups in the guest OS. It was decided to properly fix libxl_wait_for_memory_target(), and if anything improve the default behavior of apps using the freemem reference impl in xl. xl was patched to accommodate the change in libxl_wait_for_memory_target() with xen.git commit 883b30a0. This patch does the same in the libxl driver. While at it, I changed the logic to essentially match freemem() in $xensrc/tools/libxl/xl_cmdimpl.c. It was a bit cleaner IMO and will make it easier to spot future, potentially interesting divergences. |
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| docs | ||
| examples | ||
| gnulib | ||
| include | ||
| m4 | ||
| po | ||
| src | ||
| tests | ||
| tools | ||
| .ctags | ||
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| .gitignore | ||
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| .mailmap | ||
| AUTHORS.in | ||
| autobuild.sh | ||
| autogen.sh | ||
| bootstrap | ||
| bootstrap.conf | ||
| cfg.mk | ||
| ChangeLog-old | ||
| config-post.h | ||
| configure.ac | ||
| COPYING | ||
| COPYING.LESSER | ||
| HACKING | ||
| libvirt-lxc.pc.in | ||
| libvirt-qemu.pc.in | ||
| libvirt.pc.in | ||
| libvirt.spec.in | ||
| Makefile.am | ||
| Makefile.nonreentrant | ||
| mingw-libvirt.spec.in | ||
| README | ||
| README-hacking | ||
| run.in | ||
| TODO | ||
LibVirt : simple API for virtualization
Libvirt is a C toolkit to interact with the virtualization capabilities
of recent versions of Linux (and other OSes). It is free software
available under the GNU Lesser General Public License. Virtualization of
the Linux Operating System means the ability to run multiple instances of
Operating Systems concurrently on a single hardware system where the basic
resources are driven by a Linux instance. The library aim at providing
long term stable C API initially for the Xen paravirtualization but
should be able to integrate other virtualization mechanisms if needed.
Daniel Veillard <veillard@redhat.com>