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[libvirt] [PATCH v2 1/3] libxl: implement NUMA capabilities reporting



Starting from Xen 4.2, libxl has all the bits and pieces in place
for retrieving an adequate amount of information about the host
NUMA topology. It is therefore possible, after a bit of shuffling,
to arrange those information in the way libvirt wants to present
them to the outside world.

Therefore, with this patch, the <topology> section of the host
capabilities is properly populated, when running on Xen, so that
we can figure out whether or not we're running on a NUMA host,
and what its characteristics are.

[raistlin Zhaman ~]$ sudo virsh --connect xen:/// capabilities
<capabilities>
  <host>
    <cpu>
    ....
    <topology>
      <cells num='2'>
        <cell id='0'>
          <memory unit='KiB'>6291456</memory>
          <cpus num='8'>
            <cpu id='0' socket_id='1' core_id='0' siblings='0-1'/>
            <cpu id='1' socket_id='1' core_id='0' siblings='0-1'/>
            <cpu id='2' socket_id='1' core_id='1' siblings='2-3'/>
            <cpu id='3' socket_id='1' core_id='1' siblings='2-3'/>
            <cpu id='4' socket_id='1' core_id='9' siblings='4-5'/>
            <cpu id='5' socket_id='1' core_id='9' siblings='4-5'/>
            <cpu id='6' socket_id='1' core_id='10' siblings='6-7'/>
            <cpu id='7' socket_id='1' core_id='10' siblings='6-7'/>
          </cpus>
        </cell>
        <cell id='1'>
          <memory unit='KiB'>6881280</memory>
          <cpus num='8'>
            <cpu id='8' socket_id='0' core_id='0' siblings='8-9'/>
            <cpu id='9' socket_id='0' core_id='0' siblings='8-9'/>
            <cpu id='10' socket_id='0' core_id='1' siblings='10-11'/>
            <cpu id='11' socket_id='0' core_id='1' siblings='10-11'/>
            <cpu id='12' socket_id='0' core_id='9' siblings='12-13'/>
            <cpu id='13' socket_id='0' core_id='9' siblings='12-13'/>
            <cpu id='14' socket_id='0' core_id='10' siblings='14-15'/>
            <cpu id='15' socket_id='0' core_id='10' siblings='14-15'/>
          </cpus>
        </cell>
      </cells>
    </topology>
  </host>
  ....

Signed-off-by: Dario Faggioli <dario faggioli citrix com>
---
Changes from v1:
 * fixed a typo in the commit message, as requested during review;
 * fixed coding style (one function parameters per line and no spaces
   between variable definitions), as requested during review;
 * avoid zero-filling memory after VIR_ALLOC_N(), since it does that
   already, as requested during review;
 * improved out of memory error reporting, as requested during review;
 * libxlMakeNumaCapabilities() created, accommodating all the NUMA
   related additions, instead of having them within
   libxlMakeCapabilitiesInternal(), as suggested during review.
---
 src/libxl/libxl_conf.c |  141 ++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 140 insertions(+), 1 deletion(-)

diff --git a/src/libxl/libxl_conf.c b/src/libxl/libxl_conf.c
index e170357..7515995 100644
--- a/src/libxl/libxl_conf.c
+++ b/src/libxl/libxl_conf.c
@@ -161,6 +161,115 @@ libxlBuildCapabilities(virArch hostarch,
 }
 
 static virCapsPtr
+libxlMakeNumaCapabilities(libxl_numainfo *numa_info,
+                          int nr_nodes,
+                          libxl_cputopology *cpu_topo,
+                          int nr_cpus,
+                          virCapsPtr caps)
+{
+    virCapsHostNUMACellCPUPtr *cpus = NULL;
+    int *nr_cpus_node = NULL;
+    bool numa_failed = false;
+    int i;
+
+    if (VIR_ALLOC_N(cpus, nr_nodes)) {
+        virReportOOMError();
+        return caps;
+    }
+
+    if (VIR_ALLOC_N(nr_cpus_node, nr_nodes)) {
+        VIR_FREE(cpus);
+        virReportOOMError();
+        return caps;
+    }
+
+    /* For each node, prepare a list of CPUs belonging to that node */
+    for (i = 0; i < nr_cpus; i++) {
+        int node = cpu_topo[i].node;
+
+        if (cpu_topo[i].core == LIBXL_CPUTOPOLOGY_INVALID_ENTRY)
+            continue;
+
+        nr_cpus_node[node]++;
+
+        if (nr_cpus_node[node] == 1) {
+            if (VIR_ALLOC(cpus[node]) < 0) {
+                virReportOOMError();
+                numa_failed = true;
+                goto cleanup;
+            }
+        }
+        else {
+            if (VIR_REALLOC_N(cpus[node], nr_cpus_node[node]) < 0) {
+                virReportOOMError();
+                numa_failed = true;
+                goto cleanup;
+            }
+        }
+
+        /* Mapping between what libxl tells and what libvirt wants */
+        cpus[node][nr_cpus_node[node]-1].id = i;
+        cpus[node][nr_cpus_node[node]-1].socket_id = cpu_topo[i].socket;
+        cpus[node][nr_cpus_node[node]-1].core_id = cpu_topo[i].core;
+        /* Allocate the siblings maps. We will be filling them later */
+        cpus[node][nr_cpus_node[node]-1].siblings = virBitmapNew(nr_cpus);
+        if (!cpus[node][nr_cpus_node[node]-1].siblings) {
+            virReportOOMError();
+            numa_failed = true;
+            goto cleanup;
+        }
+    }
+
+    /* Let's now populate the siblings bitmaps */
+    for (i = 0; i < nr_cpus; i++) {
+        int j, node = cpu_topo[i].node;
+
+        if (cpu_topo[i].core == LIBXL_CPUTOPOLOGY_INVALID_ENTRY)
+            continue;
+
+        for (j = 0; j < nr_cpus_node[node]; j++) {
+            if (cpus[node][j].core_id == cpu_topo[i].core)
+                ignore_value(virBitmapSetBit(cpus[node][j].siblings, i));
+        }
+    }
+
+    for (i = 0; i < nr_nodes; i++) {
+        if (numa_info[i].size == LIBXL_NUMAINFO_INVALID_ENTRY)
+            continue;
+
+        if (virCapabilitiesAddHostNUMACell(caps, i, nr_cpus_node[i],
+                                           numa_info[i].size / 1024,
+                                           cpus[i]) < 0) {
+            virCapabilitiesClearHostNUMACellCPUTopology(cpus[i],
+                                                        nr_cpus_node[i]);
+            numa_failed = true;
+            goto cleanup;
+        }
+
+        /* This is safe, as the CPU list is now stored in the NUMA cell */
+        cpus[i] = NULL;
+    }
+
+ cleanup:
+
+    if (numa_failed) {
+        /* Looks like something went wrong. Well, that's bad, but probably
+         * not enough to break the whole driver, so we log and carry on */
+        for (i = 0; i < nr_nodes; i++) {
+            VIR_FREE(cpus[i]);
+        }
+        VIR_WARN("Failed to retrieve and build host NUMA topology properly,\n"
+                 "disabling NUMA capabilities");
+        virCapabilitiesFreeNUMAInfo(caps);
+    }
+
+    VIR_FREE(cpus);
+    VIR_FREE(nr_cpus_node);
+
+    return caps;
+}
+
+static virCapsPtr
 libxlMakeCapabilitiesInternal(virArch hostarch,
                               libxl_physinfo *phy_info,
                               char *capabilities)
@@ -772,7 +881,11 @@ libxlMakeCapabilities(libxl_ctx *ctx)
 {
     int err;
     libxl_physinfo phy_info;
+    libxl_numainfo *numa_info = NULL;
+    libxl_cputopology *cpu_topo = NULL;
     const libxl_version_info *ver_info;
+    int nr_nodes = 0, nr_cpus = 0;
+    virCapsPtr caps;
 
     err = regcomp(&xen_cap_rec, xen_cap_re, REG_EXTENDED);
     if (err != 0) {
@@ -796,9 +909,35 @@ libxlMakeCapabilities(libxl_ctx *ctx)
         return NULL;
     }
 
-    return libxlMakeCapabilitiesInternal(virArchFromHost(),
+    /* Let's try to fetch NUMA info, but it is not critical if we fail */
+    numa_info = libxl_get_numainfo(ctx, &nr_nodes);
+    if (numa_info == NULL)
+        VIR_WARN("libxl_get_numainfo failed to retrieve NUMA data");
+    else {
+        /* If the above failed, we'd have no NUMa caps anyway! */
+        cpu_topo = libxl_get_cpu_topology(ctx, &nr_cpus);
+        if (cpu_topo == NULL) {
+            VIR_WARN("libxl_get_cpu_topology failed to retrieve topology");
+            libxl_numainfo_list_free(numa_info, nr_nodes);
+        }
+    }
+
+    caps = libxlMakeCapabilitiesInternal(virArchFromHost(),
                                          &phy_info,
                                          ver_info->capabilities);
+
+    /* Add topology information to caps, if available */
+    if (numa_info && cpu_topo)
+        caps = libxlMakeNumaCapabilities(numa_info,
+                                         nr_nodes,
+                                         cpu_topo,
+                                         nr_cpus,
+                                         caps);
+
+    libxl_cputopology_list_free(cpu_topo, nr_cpus);
+    libxl_numainfo_list_free(numa_info, nr_nodes);
+
+    return caps;
 }
 
 int


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