[libvirt] [PATCH] Implement CPU topology support for QEMU driver
Jiri Denemark
jdenemar at redhat.com
Wed Jan 13 08:47:00 UTC 2010
> > ADD_ARG_LIT("-smp");
> > - ADD_ARG_LIT(vcpus);
> > + if ((qemuCmdFlags & QEMUD_CMD_FLAG_SMP_TOPOLOGY) && def->cpu) {
> > + virBuffer buf = VIR_BUFFER_INITIALIZER;
> > +
> > + virBufferVSprintf(&buf, "%lu", def->vcpus);
> > +
> > + if (def->cpu->sockets > 0)
> > + virBufferVSprintf(&buf, ",sockets=%u", def->cpu->sockets);
> > +
> > + if (def->cpu->cores > 0)
> > + virBufferVSprintf(&buf, ",cores=%u", def->cpu->cores);
> > +
> > + if (def->cpu->threads > 0)
> > + virBufferVSprintf(&buf, ",threads=%u", def->cpu->threads);
> > +
> > + if (virBufferError(&buf)) {
> > + virBufferFreeAndReset(&buf);
> > + goto no_memory;
> > + }
> > +
> > + ADD_ARG(virBufferContentAndReset(&buf));
> > + }
> > + else {
> > + char vcpus[50];
> > + snprintf(vcpus, sizeof(vcpus), "%lu", def->vcpus);
> > + ADD_ARG_LIT(vcpus);
> > + }
>
>
> Can you split this piece of code out into a separate method with a
> signature like
>
> static char *qemuBuildCPUStr(virDomainDefPtr def, int qemuCmdFlags);
>
> The main qemuBuildCommandLine method is getting out of control :-)
With pleasure.
> Also, in the case where 'def->cpu' is NULL, but QEMUD_CMD_FLAG_SMP_TOPOLOGY
> is available, I think we should explicitly set an arg based on
>
> sockets=def->vcpus
> cores=1
> threads=1
>
> so that we avoid relying on any changable QEMU default values.
Makes sense. I was also considering a check for vcpus == sockets * cores *
threads, but I'm not totally convinced it is a good idea.
> > + do {
> > + if (*p == '\0' || *p == ',')
> > + goto syntax;
> > +
> > + if ((next = strchr(p, ',')))
> > + next++;
> > +
> > + if (c_isdigit(*p)) {
> > + int n;
> > + if (virStrToLong_i(p, &end, 10, &n) < 0 ||
> > + !end || (*end != ',' && *end != '\0'))
> > + goto syntax;
> > + dom->vcpus = n;
> > + } else {
> > + int i;
> > + int n = -1;
> > + for (i = 0; i < ARRAY_CARDINALITY(options); i++) {
> > + if (STRPREFIX(p, options[i])) {
> > + p += strlen(options[i]);
> > + if (virStrToLong_i(p, &end, 10, &n) < 0 ||
> > + !end || (*end != ',' && *end != '\0'))
> > + goto syntax;
> > + topology[i] = n;
> > + break;
> > + }
> > + }
> > +
> > + if (n < 0)
> > + goto syntax;
> > + }
> > + } while ((p = next));
>
> If you strip off the initial CPU count value, then you can use
>
> qemuParseCommandLineKeywords
>
> to parse the reset of the name=value args.
Ah, cool, I didn't know about it. I guess because it's not used very often in
the code. BTW, would it make sense to extend the function to (optionally)
support parsing of any comma-separated list such as keyword,name=value,...?
The "keyword" parts would result in NULL value in retvalues array and the
"name=value" parts would behave normally.
Jirka
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