On Mon, Nov 07, 2011 at 11:47:10AM -0700, Eric Blake wrote:
On 11/06/2011 06:59 AM, Bharata B Rao wrote:
qemu: Generate -numa option
From: Bharata B Rao<bharata@linux.vnet.ibm.com>
Add routines to generate -numa QEMU command line option based on <numa> ...</numa> XML specifications.
Signed-off-by: Bharata B Rao<bharata@linux.vnet.ibm.com>
+static int +qemuBuildNumaCPUArgStr(char *cpumask, virBufferPtr buf) +{ + int i, first, last; + int cpuSet = 0; +
What happens if cpumask is all 0?
+ for (i = 0; i< VIR_DOMAIN_CPUMASK_LEN; i++) { + if (cpumask[i]) {
This if branch is skipped,
+ if (cpuSet) + last = i; + else { + first = last = i; + cpuSet = 1; + } + } else { + if (!cpuSet) + continue;
so this branch always continues,
+ if (first == last) + virBufferAsprintf(buf, "%d,", first); + else + virBufferAsprintf(buf, "%d-%d,", first, last); + cpuSet = 0; + } + } + + if (cpuSet) {
and this if is skipped,
+ if (first == last) + virBufferAsprintf(buf, "%d,", first); + else + virBufferAsprintf(buf, "%d-%d,", first, last); + } + + /* Remove the trailing comma */ + return virBufferTruncate(buf, 1);
meaning that nothing was appended to buf, and you are now stripping unknown text, rather than a comma you just added. Do we need a sanity check to ensure that the cpumask specifies at least one cpu? And if so, would that mask be better here, or up front at the xml parsing time?
Good catch. I am now ensuring that this doesn't get a mask with no cpus.
+} + +static int +qemuBuildNumaArgStr(const virDomainDefPtr def, virCommandPtr cmd) +{ + int i; + char *node; + virBuffer buf = VIR_BUFFER_INITIALIZER; + + for (i = 0; i< def->cpu->ncells; i++) { + virCommandAddArg(cmd, "-numa"); + virBufferAsprintf(&buf, "%s", "node");
More efficient as virBufferAddLit(&buf, "node"), or...
Right.
+ virBufferAsprintf(&buf, ",nodeid=%d", def->cpu->cells[i].cellid);
merge these two into a single:
virBufferAsprintf(&buf, "node,nodeid=%d", ...);
+ virBufferAsprintf(&buf, ",cpus=");
Again, with no % in the format string, it is more efficient to use virBufferAddLit.
+ + if (qemuBuildNumaCPUArgStr(def->cpu->cells[i].cpumask,&buf))
Generally, we prefer an explicit < 0 comparison when checking for failure.
Ok as you prefer :)
+ goto error; + + virBufferAsprintf(&buf, ",mems=%d", def->cpu->cells[i].mem); +
Why do we need to bother with stripping a trailing comma in qemuBuildNumaCPUArgStr, if we will just be adding a comma back again here as the very next statement? You could skip all the hassle of adding virBufferTruncate by just transferring the comma out of this statement and into qemuBuildNumaCPUArgStr
This is what I mentioned in my last iteration. But since you hinted at extending virBuffer, I went on that path. Another motivation was to keep qemuBuildNumaArgStr() generic enough so that it gives out comma/dash separate CPU string without the ending comma in case this functionality is needed elsewhere in libvirt. But I guess I will stick with not appending comma to "memory" in which case this extension to virBuffer isn't needed.
(that said, I still think virBufferTruncate will be a useful addition in other contexts).
I think we should add virBufferTruncate only when we get any user for that. Hence I am not including virBufferTruncate in v3 patchset.
+ if (virBufferError(&buf)) + goto error; + + node = virBufferContentAndReset(&buf); + virCommandAddArg(cmd, node); + VIR_FREE(node);
It's more efficient to replace these five lines with one:
virCommandAddArgBuffer(cmd, &buf);
I can't because this is in a loop and I want to break out from the loop in case of buffer error. virCommandAddArgBuffer doesn't allow that. But I did replace the last 3 lines with virCommandAddArgBuffer :)
@@ -3414,6 +3482,9 @@ qemuBuildCommandLine(virConnectPtr conn, virCommandAddArg(cmd, smp); VIR_FREE(smp);
+ if (def->cpu&& def->cpu->ncells&& qemuBuildNumaArgStr(def, cmd))
Again, explicit < 0 check when looking for errors.
Sure.
+<topology sockets="2" cores="4" threads="2"/> +<numa> +<cell cpus="0-7" mems="109550"/> +<cell cpus="8-15" mems="109550"/>
Of course, this will need tweaking to match any XML changes made in 1/3, but thanks for adding test cases!
Tweaked the testcases. BTW the testcases were useful to me as they uncovered 2 bugs in my code!
Overall, I think we'll need a v3 (you may want to use git send-email --subject-prefix=PATCHv3; it wasn't very clear from the subject line that this was already a v2 series), but I like where it's heading.
Will ensure [PATCH v3] for the next iteration. Thanks. v3 on its way. Regards, Bharata.