Re: [libvirt] [PATCH] qemu: Pin the emulator when only cpuset is specified

On 10/19/2012 05:45 AM, Osier Yang wrote: > On 2012年10月17日 23:38, Martin Kletzander wrote: >> According to our recent changes (clarifications), we should be pinning >> qemu's emulator processes using the<vcpu> 'cpuset' attribute in case >> there is no<emulatorpin> specified. This however doesn't work >> entirely as expected and this patch should resolve all the remaining >> issues. >> --- >> src/qemu/qemu_cgroup.c | 25 ++++++++++++++++--------- >> src/qemu/qemu_cgroup.h | 4 ++-- >> src/qemu/qemu_driver.c | 3 ++- >> src/qemu/qemu_process.c | 16 ++++++++-------- >> 4 files changed, 28 insertions(+), 20 deletions(-) >> [...] >> diff --git a/src/qemu/qemu_process.c b/src/qemu/qemu_process.c >> index a94e9c4..e08ec67 100644 >> --- a/src/qemu/qemu_process.c >> +++ b/src/qemu/qemu_process.c >> @@ -2024,11 +2024,12 @@ cleanup: >> return ret; >> } >> >> -/* Set CPU affinities for emulator threads if emulatorpin xml >> provided. */ >> +/* Set CPU affinities for emulator threads. */ >> static int >> qemuProcessSetEmulatorAffinites(virConnectPtr conn, >> virDomainObjPtr vm) >> { >> + virBitmapPtr cpumask; >> virDomainDefPtr def = vm->def; >> virNodeInfo nodeinfo; >> int ret = -1; >> @@ -2036,15 +2037,14 @@ qemuProcessSetEmulatorAffinites(virConnectPtr >> conn, >> if (virNodeGetInfo(conn,&nodeinfo) != 0) >> return -1; >> >> - if (!def->cputune.emulatorpin) >> - return 0; >> - >> - if (virProcessInfoSetAffinity(vm->pid, >> - >> def->cputune.emulatorpin->cpumask)< 0) { >> + if (def->cputune.emulatorpin) >> + cpumask = def->cputune.emulatorpin->cpumask; >> + else if (def->cpumask) >> + cpumask = def->cpumask; >> + else >> goto cleanup; >> - } >> >> - ret = 0; >> + ret = virProcessInfoSetAffinity(vm->pid, cpumask); >> cleanup: >> return ret; >> } > > This patch actually duplicates the affinity setting on domain > process with sched_setaffinity. > > Assume "cpuset" of<vcpu> is specified, and no "<emulatorpin>". > > qemuProcessInitCpuAffinity is excuted between the fork > and exec, with this patch, qemuProcessSetEmulatorAffinites > will set the affinity again using sched_setaffinity. > > Cgroup setting is fine though, as there is no previous setting > with cgroup. > > I'm wondering why the domain process is not pinned to > pCPUs specified "cpuset" of "<vcpu>" by qemuProcessInitCpuAffinity, > when<emulatorpin> is not specified. > > Regards, > Osier I'm glad you pointed it out. To be honest, it took me quite a while to see where this should be set to fix the problem with as few lines as possible. As Peter says, there is a mess with the pinning, cgroups and affinities.