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[libvirt] [PATCH 1/4] libxl: implement NUMA capabilities reporting



Starting from Xen 4.2, libxl has all the bits and pieces are 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>
---
 src/libxl/libxl_conf.c |  128 ++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 127 insertions(+), 1 deletion(-)

diff --git a/src/libxl/libxl_conf.c b/src/libxl/libxl_conf.c
index e170357..2a9bcf0 100644
--- a/src/libxl/libxl_conf.c
+++ b/src/libxl/libxl_conf.c
@@ -163,6 +163,8 @@ libxlBuildCapabilities(virArch hostarch,
 static virCapsPtr
 libxlMakeCapabilitiesInternal(virArch hostarch,
                               libxl_physinfo *phy_info,
+                              libxl_numainfo *numa_info, int nr_nodes,
+                              libxl_cputopology *cpu_topo, int nr_cpus,
                               char *capabilities)
 {
     char *str, *token;
@@ -173,6 +175,12 @@ libxlMakeCapabilitiesInternal(virArch hostarch,
     int host_pae = 0;
     struct guest_arch guest_archs[32];
     int nr_guest_archs = 0;
+
+    /* For building NUMA capabilities */
+    virCapsHostNUMACellCPUPtr *cpus = NULL;
+    int *nr_cpus_node = NULL;
+    bool numa_failed = false;
+
     virCapsPtr caps = NULL;
 
     memset(guest_archs, 0, sizeof(guest_archs));
@@ -280,6 +288,100 @@ libxlMakeCapabilitiesInternal(virArch hostarch,
                                        nr_guest_archs)) == NULL)
         goto no_memory;
 
+    /* What about NUMA? */
+    if (!numa_info || !cpu_topo)
+        return caps;
+
+    if (VIR_ALLOC_N(cpus, nr_nodes))
+        goto no_memory;
+    memset(cpus, 0, sizeof(cpus) * nr_nodes);
+
+    if (VIR_ALLOC_N(nr_cpus_node, nr_nodes)) {
+        VIR_FREE(cpus);
+        goto no_memory;
+    }
+    memset(nr_cpus_node, 0, sizeof(nr_cpus_node) * nr_nodes);
+
+    /* 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) {
+                numa_failed = true;
+                goto cleanup;
+            }
+        }
+        else {
+            if (VIR_REALLOC_N(cpus[node], nr_cpus_node[node]) < 0) {
+                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;
+        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;
 
  no_memory:
@@ -772,7 +874,11 @@ 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 +902,29 @@ 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,
+                                         numa_info, nr_nodes,
+                                         cpu_topo, nr_cpus,
                                          ver_info->capabilities);
+
+    libxl_cputopology_list_free(cpu_topo, nr_cpus);
+    libxl_numainfo_list_free(numa_info, nr_nodes);
+
+    return caps;
 }
 
 int


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