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From ca5a3f13bf247561e64ef2323b3dd28a2c3b880d Mon Sep 17 00:00:00 2001
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From: Rik van Riel <riel@redhat.com>
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Date: Thu, 12 Mar 2015 17:47:00 -0400
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Subject: [PATCH 3/3] parse isolcpus= from /proc/cmdline to set up banned_cpus
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When the user specifies a range of CPUs to be isolated from system
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tasks with isolcpus= on the kernel command line, it would be nice
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if those CPUs could automatically be excluded from getting interrupts
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routed to them, as well.
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This patch does that, by looking at /proc/cmdline
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The environment variable IRQBALANCE_BANNED_CPUS will override the
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automatically detectable banned_cpus.
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Signed-off-by: Rik van Riel <riel@redhat.com>
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---
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cputree.c | 44 ++++++++++++++++++++++++++++++++++++++++++++
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irqbalance.c | 4 ----
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2 files changed, 44 insertions(+), 4 deletions(-)
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diff --git a/cputree.c b/cputree.c
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index 8b8cf5e..cfa70b6 100644
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--- a/cputree.c
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+++ b/cputree.c
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@@ -58,6 +58,48 @@ cpumask_t cpu_possible_map;
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*/
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cpumask_t unbanned_cpus;
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+/*
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+ * By default do not place IRQs on CPUs the kernel keeps isolated,
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+ * as specified through the isolcpus= boot commandline. Users can
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+ * override this with the IRQBALANCE_BANNED_CPUS environment variable.
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+ */
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+static void setup_banned_cpus(void)
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+{
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+ FILE *file;
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+ char *c, *line = NULL;
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+ size_t size = 0;
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+ const char *isolcpus = "isolcpus=";
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+ char buffer[4096];
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+
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+ /* A manually specified cpumask overrides auto-detection. */
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+ if (getenv("IRQBALANCE_BANNED_CPUS")) {
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+ cpumask_parse_user(getenv("IRQBALANCE_BANNED_CPUS"), strlen(getenv("IRQBALANCE_BANNED_CPUS")), banned_cpus);
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+ goto out;
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+ }
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+
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+ file = fopen("/proc/cmdline", "r");
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+ if (!file)
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+ goto out;
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+
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+ if (getline(&line, &size, file) <= 0)
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+ goto out;
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+
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+ if ((c = strstr(line, isolcpus))) {
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+ char *end;
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+ int len;
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+
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+ c += strlen(isolcpus);
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+ for (end = c; *end != ' ' && *end != '\0' && *end != '\n'; end++);
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+ len = end - c;
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+
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+ cpulist_parse(c, len, banned_cpus);
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+ }
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+
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+ out:
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+ cpumask_scnprintf(buffer, 4096, banned_cpus);
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+ log(TO_CONSOLE, LOG_INFO, "Isolated CPUs: %s\n", buffer);
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+}
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+
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static struct topo_obj* add_cache_domain_to_package(struct topo_obj *cache,
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int packageid, cpumask_t package_mask)
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{
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@@ -372,6 +414,8 @@ void parse_cpu_tree(void)
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DIR *dir;
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struct dirent *entry;
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+ setup_banned_cpus();
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+
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cpus_complement(unbanned_cpus, banned_cpus);
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dir = opendir("/sys/devices/system/cpu");
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diff --git a/irqbalance.c b/irqbalance.c
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index a5079b9..e4f3b93 100644
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--- a/irqbalance.c
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+++ b/irqbalance.c
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@@ -276,10 +276,6 @@ int main(int argc, char** argv)
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*/
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openlog(argv[0], 0, LOG_DAEMON);
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- if (getenv("IRQBALANCE_BANNED_CPUS")) {
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- cpumask_parse_user(getenv("IRQBALANCE_BANNED_CPUS"), strlen(getenv("IRQBALANCE_BANNED_CPUS")), banned_cpus);
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- }
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-
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if (getenv("IRQBALANCE_ONESHOT"))
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one_shot_mode=1;
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--
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2.1.0
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