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authorHedi Berriche <hedi@sgi.com>2010-05-26 14:44:06 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2010-05-27 09:12:51 -0700
commit72680a191b934377430032f93af15ef50aafb3a8 (patch)
treee6f41babe66bf642204b3d92e793f5071739b1d2
parentbd4fb654e3a0d83ca8cb138c5e3e6e65407e119c (diff)
pids: increase pid_max based on num_possible_cpus
On a system with a substantial number of processors, the early default pid_max of 32k will not be enough. A system with 1664 CPU's, there are 25163 processes started before the login prompt. It's estimated that with 2048 CPU's we will pass the 32k limit. With 4096, we'll reach that limit very early during the boot cycle, and processes would stall waiting for an available pid. This patch increases the early maximum number of pids available, and increases the minimum number of pids that can be set during runtime. [akpm@linux-foundation.org: fix warnings] Signed-off-by: Hedi Berriche <hedi@sgi.com> Signed-off-by: Mike Travis <travis@sgi.com> Signed-off-by: Robin Holt <holt@sgi.com> Acked-by: Linus Torvalds <torvalds@linux-foundation.org> Cc: Ingo Molnar <mingo@elte.hu> Cc: Pavel Machek <pavel@ucw.cz> Cc: Alan Cox <alan@lxorguk.ukuu.org.uk> Cc: Greg KH <gregkh@suse.de> Cc: Rik van Riel <riel@redhat.com> Cc: John Stoffel <john@stoffel.org> Cc: Jack Steiner <steiner@sgi.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--include/linux/threads.h9
-rw-r--r--kernel/pid.c7
2 files changed, 16 insertions, 0 deletions
diff --git a/include/linux/threads.h b/include/linux/threads.h
index 052b12bec8b..383ab9592be 100644
--- a/include/linux/threads.h
+++ b/include/linux/threads.h
@@ -33,4 +33,13 @@
#define PID_MAX_LIMIT (CONFIG_BASE_SMALL ? PAGE_SIZE * 8 : \
(sizeof(long) > 4 ? 4 * 1024 * 1024 : PID_MAX_DEFAULT))
+/*
+ * Define a minimum number of pids per cpu. Heuristically based
+ * on original pid max of 32k for 32 cpus. Also, increase the
+ * minimum settable value for pid_max on the running system based
+ * on similar defaults. See kernel/pid.c:pidmap_init() for details.
+ */
+#define PIDS_PER_CPU_DEFAULT 1024
+#define PIDS_PER_CPU_MIN 8
+
#endif
diff --git a/kernel/pid.c b/kernel/pid.c
index aebb30d9c23..e9fd8c132d2 100644
--- a/kernel/pid.c
+++ b/kernel/pid.c
@@ -513,6 +513,13 @@ void __init pidhash_init(void)
void __init pidmap_init(void)
{
+ /* bump default and minimum pid_max based on number of cpus */
+ pid_max = min(pid_max_max, max_t(int, pid_max,
+ PIDS_PER_CPU_DEFAULT * num_possible_cpus()));
+ pid_max_min = max_t(int, pid_max_min,
+ PIDS_PER_CPU_MIN * num_possible_cpus());
+ pr_info("pid_max: default: %u minimum: %u\n", pid_max, pid_max_min);
+
init_pid_ns.pidmap[0].page = kzalloc(PAGE_SIZE, GFP_KERNEL);
/* Reserve PID 0. We never call free_pidmap(0) */
set_bit(0, init_pid_ns.pidmap[0].page);