[libvirt] [PATCH] Fix nodeinfo output on PPC64 KVM hosts
Andrea Bolognani
abologna at redhat.com
Mon Jun 29 12:11:54 UTC 2015
On Thu, 2016-06-25 at 12:03 +0530, Shivaprasad G Bhat wrote:
Hi Shivaprasad,
here are a few comments about your patch.
>
[...]
> +# if HAVE_LINUX_KVM_H
> +# include <linux/kvm.h>
This line should be moved to the top of the file, with all the other
#include directives.
> + kvmfd = open("/dev/kvm", O_RDONLY);
> + if (kvmfd >= 0) {
> +# ifdef KVM_CAP_PPC_SMT
> + valid_ppc64_kvmhost_mode = true;
> + /* For Phyp and KVM based guests the ioctl for
> KVM_CAP_PPC_SMT
> + * returns zero and both primary and secondary threads
> will be
> + * online. Dont try to alter or interpret anything here.
> + */
> + threads_per_subcore = ioctl(kvmfd, KVM_CHECK_EXTENSION,
> KVM_CAP_PPC_SMT);
> + if (threads_per_subcore == 0)
> + valid_ppc64_kvmhost_mode = false;
> +# endif
> + }
> + VIR_FORCE_CLOSE(kvmfd);
> +# endif
> + rewinddir(cpudir);
> + lastonline = -1;
> + while (valid_ppc64_kvmhost_mode &&
> + ((direrr = virDirRead(cpudir, &cpudirent, node)) >
> 0)) {
> + if (sscanf(cpudirent->d_name, "cpu%u", &cpu) != 1)
> + continue;
> + if ((online = virNodeGetCpuValue(node, cpu, "online",
> 1)) < 0)
> + goto cleanup;
> +
> + if (online) {
> + if (lastonline != -1 &&
> + (cpu - lastonline) < threads_per_subcore) {
> + valid_ppc64_kvmhost_mode = false; /* if any of
> secondaries
> + * online */
If a comment is long enough to span two lines, it should probably not
start at the end of a statement but rather be above it.
> + break;
> + }
> + lastonline = cpu;
> + }
> + }
> + }
> +
Enclosing this whole block within the #if and #ifdef directives would
make
the code cleaner; on the other hand, since the skeleton of the loop is
identical to the one a few lines above, maybe you could move the part
reading from /dev/kvm closer to the top and merge the two loops
together?
> /* allocate cpu maps for each socket */
> if (VIR_ALLOC_N(core_maps, sock_max) < 0)
> goto cleanup;
> @@ -473,6 +539,7 @@ virNodeParseNode(const char *node,
>
> /* iterate over all CPU's in the node */
> rewinddir(cpudir);
> + lastonline = -1;
> while ((direrr = virDirRead(cpudir, &cpudirent, node)) > 0) {
> if (sscanf(cpudirent->d_name, "cpu%u", &cpu) != 1)
> continue;
> @@ -480,6 +547,17 @@ virNodeParseNode(const char *node,
> if ((online = virNodeGetCpuValue(node, cpu, "online", 1)) <
> 0)
> goto cleanup;
>
> + if (ARCH_IS_PPC64(arch) && valid_ppc64_kvmhost_mode) {
valid_ppc64_kvmhost_mode can be true iff ARCH_IS_PPC64(arch), so this
condition is kinda redundant.
> + if (online) {
> + lastonline = cpu;
> + } else if (lastonline != -1 &&
> + (cpu-lastonline) < threads_per_subcore) {
> + processors++; /* Count only those secondaries whose
> primary
> + subcore is online */
Same as above.
> + continue;
> + }
> + }
> +
> if (!online) {
> (*offline)++;
> continue;
> @@ -528,6 +606,13 @@ virNodeParseNode(const char *node,
> *cores = core;
> }
>
> + if (ARCH_IS_PPC64(arch) && valid_ppc64_kvmhost_mode) {
Same as above.
> + /* The actual host threads per core is
> + * multiple of the subcores_per_core(i.e variable *threads
> in this case)
> + * and threads_per_subcore.
> + */
> + *threads = *threads * threads_per_subcore;
> + }
> ret = processors;
>
> cleanup:
>
Overall, the code makes sense and seems to work from my limited
testing.
However, this change completely breaks the topology information
reported
by `virsh capabilities`. Here's the output on a host with
subcores_per_core=1, without the patch:
<topology>
<cells num='4'>
<cell id='0'>
<memory unit='KiB'>67108864</memory>
<pages unit='KiB' size='64'>1048576</pages>
<pages unit='KiB' size='16384'>0</pages>
<pages unit='KiB' size='16777216'>0</pages>
<distances>
<sibling id='0' value='10'/>
<sibling id='1' value='20'/>
<sibling id='16' value='40'/>
<sibling id='17' value='40'/>
</distances>
<cpus num='5'>
<cpu id='0' socket_id='0' core_id='32' siblings='0'/>
<cpu id='8' socket_id='0' core_id='40' siblings='8'/>
<cpu id='16' socket_id='0' core_id='48' siblings='16'/>
<cpu id='24' socket_id='0' core_id='96' siblings='24'/>
<cpu id='32' socket_id='0' core_id='104' siblings='32'/>
</cpus>
</cell>
<cell id='1'>
<memory unit='KiB'>67108864</memory>
<pages unit='KiB' size='64'>1048576</pages>
<pages unit='KiB' size='16384'>0</pages>
<pages unit='KiB' size='16777216'>0</pages>
<distances>
<sibling id='0' value='20'/>
<sibling id='1' value='10'/>
<sibling id='16' value='40'/>
<sibling id='17' value='40'/>
</distances>
<cpus num='5'>
<cpu id='40' socket_id='1' core_id='160' siblings='40'/>
<cpu id='48' socket_id='1' core_id='168' siblings='48'/>
<cpu id='56' socket_id='1' core_id='176' siblings='56'/>
<cpu id='64' socket_id='1' core_id='224' siblings='64'/>
<cpu id='72' socket_id='1' core_id='232' siblings='72'/>
</cpus>
</cell>
<cell id='16'>
<memory unit='KiB'>67108864</memory>
<pages unit='KiB' size='64'>1048576</pages>
<pages unit='KiB' size='16384'>0</pages>
<pages unit='KiB' size='16777216'>0</pages>
<distances>
<sibling id='0' value='40'/>
<sibling id='1' value='40'/>
<sibling id='16' value='10'/>
<sibling id='17' value='20'/>
</distances>
<cpus num='5'>
<cpu id='80' socket_id='16' core_id='2088' siblings='80'/>
<cpu id='88' socket_id='16' core_id='2096' siblings='88'/>
<cpu id='96' socket_id='16' core_id='2144' siblings='96'/>
<cpu id='104' socket_id='16' core_id='2152'
siblings='104'/>
<cpu id='112' socket_id='16' core_id='2160'
siblings='112'/>
</cpus>
</cell>
<cell id='17'>
<memory unit='KiB'>67108864</memory>
<pages unit='KiB' size='64'>1048576</pages>
<pages unit='KiB' size='16384'>0</pages>
<pages unit='KiB' size='16777216'>0</pages>
<distances>
<sibling id='0' value='40'/>
<sibling id='1' value='40'/>
<sibling id='16' value='20'/>
<sibling id='17' value='10'/>
</distances>
<cpus num='5'>
<cpu id='120' socket_id='17' core_id='2208'
siblings='120'/>
<cpu id='128' socket_id='17' core_id='2216'
siblings='128'/>
<cpu id='136' socket_id='17' core_id='2272'
siblings='136'/>
<cpu id='144' socket_id='17' core_id='2280'
siblings='144'/>
<cpu id='152' socket_id='17' core_id='2288'
siblings='152'/>
</cpus>
</cell>
</cells>
</topology>
With the patch:
<topology>
<cells num='1'>
<cell id='0'>
<memory unit='KiB'>263635136</memory>
<cpus num='160'>
<cpu id='0' socket_id='0' core_id='0' siblings='0'/>
<cpu id='8' socket_id='0' core_id='1' siblings='8'/>
<cpu id='16' socket_id='0' core_id='2' siblings='16'/>
<cpu id='24' socket_id='0' core_id='3' siblings='24'/>
<cpu id='32' socket_id='0' core_id='4' siblings='32'/>
<cpu id='0'/>
<!-- The above line is repeated 155 times -->
</cpus>
</cell>
</cells>
</topology>
This issue needs to be addressed before the changes can be considered
for inclusion. I'd also highly recommend writing tests cases in order
to prevent regressions in the future.
Cheers.
--
Andrea Bolognani
Software Engineer - Virtualization Team
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