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From: Prarit Bhargava <prarit@redhat.com>
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Subject: linux: fix support for NUMA node0 being offline
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commit 0114c2b0b3e39265e0829eebfff87ac9f4412fe9
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Author: Brice Goglin <Brice.Goglin@inria.fr>
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Date: Mon Apr 26 20:35:42 2021 +0200
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linux: fix support for NUMA node0 being offline
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Just like we didn't support offline CPU#0 until commit
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7bcc273efd50536961ba16d474efca4ae163229b, we need to
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support node0 being offline as well.
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It's not clear whether it's a new Linux feature or not,
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this was reported on a POWER LPAR VM.
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The symptoms are different here because we got no NUMA
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nodes at all, hence the core hwloc added a default
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machine-wide node. But this node got marked disallowed
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by Linux cgroups. Hence load() failed with
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"Topology does not contain any NUMA node, aborting!"
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We opportunistically assume node0 is online to avoid
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the overhead in the vast majority of cases. If node0
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is missing, we parse "online" to find the first node.
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Thanks to Jirka Hladky for the report.
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Signed-off-by: Brice Goglin <Brice.Goglin@inria.fr>
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Signed-off-by: Prarit Bhargava <prarit@redhat.com>
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diff -urNp hwloc-2.2.0.orig/hwloc/topology-linux.c hwloc-2.2.0/hwloc/topology-linux.c
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--- hwloc-2.2.0.orig/hwloc/topology-linux.c 2021-05-10 14:44:42.690559128 -0400
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+++ hwloc-2.2.0/hwloc/topology-linux.c 2021-05-10 14:44:57.858982883 -0400
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@@ -5342,6 +5342,9 @@ static const char *find_sysfs_cpu_path(i
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static const char *find_sysfs_node_path(int root_fd)
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{
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+ unsigned first;
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+ int err;
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+
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if (!hwloc_access("/sys/bus/node/devices", R_OK|X_OK, root_fd)
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&& !hwloc_access("/sys/bus/node/devices/node0/cpumap", R_OK, root_fd))
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return "/sys/bus/node/devices";
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@@ -5350,6 +5353,28 @@ static const char *find_sysfs_node_path(
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&& !hwloc_access("/sys/devices/system/node/node0/cpumap", R_OK, root_fd))
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return "/sys/devices/system/node";
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+ /* node0 might be offline, fallback to looking at the first online node.
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+ * online contains comma-separated ranges, just read the first number.
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+ */
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+ hwloc_debug("Failed to find sysfs node files using node0, looking at online nodes...\n");
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+ err = hwloc_read_path_as_uint("/sys/devices/system/node/online", &first, root_fd);
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+ if (err) {
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+ hwloc_debug("Failed to find read /sys/devices/system/node/online.\n");
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+ } else {
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+ char path[PATH_MAX];
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+ hwloc_debug("Found node#%u as first online node\n", first);
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+
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+ snprintf(path, sizeof(path), "/sys/bus/node/devices/node%u/cpumap", first);
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+ if (!hwloc_access("/sys/bus/node/devices", R_OK|X_OK, root_fd)
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+ && !hwloc_access(path, R_OK, root_fd))
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+ return "/sys/bus/node/devices";
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+
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+ snprintf(path, sizeof(path), "/sys/devices/system/node/node%u/cpumap", first);
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+ if (!hwloc_access("/sys/devices/system/node", R_OK|X_OK, root_fd)
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+ && !hwloc_access(path, R_OK, root_fd))
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+ return "/sys/devices/system/node";
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+ }
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+
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return NULL;
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}
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