Re: [libvirt] [PATCH 2/3] qemu_driver: clamp value for setting sched cpu_shares with --config.

As shown in 'man virsh' about schedinfo: Note: The cpu_shares parameter has a valid value range of 0-262144; Negative values are wrapped to positive, and larger values are capped at the maximum. Therefore, -1 is a useful shorthand for 262144. On the Linux kernel, the values 0 and 1 are automatically converted to a minimal value of 2. it works well with --live, but not with --config. Example: # virsh schedinfo rhel7-ful --set cpu_shares=0 --config Scheduler : posix cpu_shares : 0 vcpu_period : 0 vcpu_quota : 0 emulator_period: 0 emulator_quota : 0 cpu_shares is 0 rather than expected 2. What's worse, when we start it again, it is the default value of cpu_shares 1024. Because when we set the value of cpu_shares, when flag is --live, write the value into cgroup/cpu.shares. Then it will convert the value into the range of [2, 262144]. When flag is --config, we set the value into vmdef immidiately and 0 means no settting for cpu_shares. When we start vm again, libvirt use default value(1024) for it. This patch clamp the cpu_shares value when flag is --config, then we will get then "correct" settting in output of virsh schedinfo and value in cgroup after next booting of vm.

Signed-off-by: Dongsheng Yang <yangds.fnst(a)cn.fujitsu.com&gt; --- src/qemu/qemu_driver.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c index 52ca47c..7648865 100644 --- a/src/qemu/qemu_driver.c +++ b/src/qemu/qemu_driver.c @@ -112,6 +112,8 @@ VIR_LOG_INIT("qemu.qemu_driver"); #define QEMU_SCHED_MAX_PERIOD 1000000LL #define QEMU_SCHED_MIN_QUOTA 1000LL #define QEMU_SCHED_MAX_QUOTA 18446744073709551LL +#define QEMU_SCHED_MIN_SHARES 2LL +#define QEMU_SCHED_MAX_SHARES 262144LL #if HAVE_LINUX_KVM_H # include <linux/kvm.h> @@ -9063,7 +9065,9 @@ qemuDomainSetSchedulerParametersFlags(virDomainPtr dom, } if (flags & VIR_DOMAIN_AFFECT_CONFIG) { - vmdef->cputune.shares = value_ul; + vmdef->cputune.shares = CLAMP(value_ul, + QEMU_SCHED_MIN_SHARES, + QEMU_SCHED_MAX_SHARES); vmdef->cputune.sharesSpecified = true; } -- 1.8.2.1 -- libvir-list mailing list libvir-list(a)redhat.com https://www.redhat.com/mailman/listinfo/libvir-list