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



On 2012年10月19日 11:45, 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_cgroup.c b/src/qemu/qemu_cgroup.c
index 166f9b9..6b94686 100644
--- a/src/qemu/qemu_cgroup.c
+++ b/src/qemu/qemu_cgroup.c
@@ -501,7 +501,7 @@ int qemuSetupCgroupVcpuPin(virCgroupPtr cgroup,

for (i = 0; i< nvcpupin; i++) {
if (vcpuid == vcpupin[i]->vcpuid) {
- return qemuSetupCgroupEmulatorPin(cgroup, vcpupin[i]);
+ return qemuSetupCgroupEmulatorPin(cgroup, vcpupin[i]->cpumask);
}
}

@@ -509,12 +509,12 @@ int qemuSetupCgroupVcpuPin(virCgroupPtr cgroup,
}

int qemuSetupCgroupEmulatorPin(virCgroupPtr cgroup,
- virDomainVcpuPinDefPtr vcpupin)
+ virBitmapPtr cpumask)
{
int rc = 0;
char *new_cpus = NULL;

- new_cpus = virBitmapFormat(vcpupin->cpumask);
+ new_cpus = virBitmapFormat(cpumask);
if (!new_cpus) {
virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
_("failed to convert cpu mask"));
@@ -643,6 +643,7 @@ cleanup:
int qemuSetupCgroupForEmulator(struct qemud_driver *driver,
virDomainObjPtr vm)
{
+ virBitmapPtr cpumask = NULL;
virCgroupPtr cgroup = NULL;
virCgroupPtr cgroup_emulator = NULL;
virDomainDefPtr def = vm->def;
@@ -690,12 +691,18 @@ int qemuSetupCgroupForEmulator(struct
qemud_driver *driver,
}
}

- if (def->cputune.emulatorpin&&
- qemuCgroupControllerActive(driver, VIR_CGROUP_CONTROLLER_CPUSET)) {
- rc = qemuSetupCgroupEmulatorPin(cgroup_emulator,
- def->cputune.emulatorpin);
- if (rc< 0)
- goto cleanup;
+ if (def->cputune.emulatorpin)
+ cpumask = def->cputune.emulatorpin->cpumask;
+ else if (def->cpumask)
+ cpumask = def->cpumask;
+
+ if (cpumask) {
+ if (qemuCgroupControllerActive(driver, VIR_CGROUP_CONTROLLER_CPUSET)) {
+ rc = qemuSetupCgroupEmulatorPin(cgroup_emulator, cpumask);
+ if (rc< 0)
+ goto cleanup;
+ }
+ cpumask = NULL; /* sanity */
}

if (period || quota) {
diff --git a/src/qemu/qemu_cgroup.h b/src/qemu/qemu_cgroup.h
index b7b0211..362080a 100644
--- a/src/qemu/qemu_cgroup.h
+++ b/src/qemu/qemu_cgroup.h
@@ -1,7 +1,7 @@
/*
* qemu_cgroup.h: QEMU cgroup management
*
- * Copyright (C) 2006-2007, 2009-2011 Red Hat, Inc.
+ * Copyright (C) 2006-2007, 2009-2012 Red Hat, Inc.
* Copyright (C) 2006 Daniel P. Berrange
*
* This library is free software; you can redistribute it and/or
@@ -57,7 +57,7 @@ int qemuSetupCgroupVcpuPin(virCgroupPtr cgroup,
virDomainVcpuPinDefPtr *vcpupin,
int nvcpupin,
int vcpuid);
-int qemuSetupCgroupEmulatorPin(virCgroupPtr cgroup,
virDomainVcpuPinDefPtr vcpupin);
+int qemuSetupCgroupEmulatorPin(virCgroupPtr cgroup, virBitmapPtr
cpumask);
int qemuSetupCgroupForVcpu(struct qemud_driver *driver,
virDomainObjPtr vm);
int qemuSetupCgroupForEmulator(struct qemud_driver *driver,
virDomainObjPtr vm);
diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
index fa37bfd..adfbfa6 100644
--- a/src/qemu/qemu_driver.c
+++ b/src/qemu/qemu_driver.c
@@ -4245,7 +4245,8 @@ qemudDomainPinEmulator(virDomainPtr dom,
if (virCgroupForDomain(driver->cgroup, vm->def->name,
&cgroup_dom, 0) == 0) {
if (virCgroupForEmulator(cgroup_dom,&cgroup_emulator, 0) == 0) {
- if (qemuSetupCgroupEmulatorPin(cgroup_emulator, newVcpuPin[0])< 0) {
+ if (qemuSetupCgroupEmulatorPin(cgroup_emulator,
+ newVcpuPin[0]->cpumask)< 0) {
virReportError(VIR_ERR_OPERATION_INVALID, "%s",
_("failed to set cpuset.cpus in cgroup"
" for emulator threads"));
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


Just realized this patch actually introduced regression,

Assumes XML like:

<vcpu placement="auto">10</vcpu>

Which expects the domain process is pinned to the nodeset
returned from numad, however, the qemuProcessSetEmulatorAffinites
will override the previous pinning with all available pCPUs.

Because:

>> + if (def->cputune.emulatorpin)
>> + cpumask = def->cputune.emulatorpin->cpumask;
>> + else if (def->cpumask)
>> + cpumask = def->cpumask;

Regards,
Osier


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