The patch titled
pids: increase pid_max based on num_possible_cpus
has been added to the -mm tree. Its filename is
pids-increase-pid_max-based-on-num_possible_cpus.patch
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------------------------------------------------------
Subject: pids: increase pid_max based on num_possible_cpus
From: Mike Travis <travis@xxxxxxx>
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.
Signed-off-by: Hedi Berriche <hedi@xxxxxxx>
Signed-off-by: Mike Travis <travis@xxxxxxx>
Signed-off-by: Robin Holt <holt@xxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxx>
Cc: Pavel Machek <pavel@xxxxxx>
Cc: Alan Cox <alan@xxxxxxxxxxxxxxxxxxx>
Cc: Greg KH <gregkh@xxxxxxx>
Cc: Rik van Riel <riel@xxxxxxxxxx>
Cc: John Stoffel <john@xxxxxxxxxxx>
Cc: Jack Steiner <steiner@xxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/threads.h | 9 +++++++++
kernel/pid.c | 7 +++++++
2 files changed, 16 insertions(+)
diff -puN include/linux/threads.h~pids-increase-pid_max-based-on-num_possible_cpus include/linux/threads.h
--- a/include/linux/threads.h~pids-increase-pid_max-based-on-num_possible_cpus
+++ a/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 -puN kernel/pid.c~pids-increase-pid_max-based-on-num_possible_cpus kernel/pid.c
--- a/kernel/pid.c~pids-increase-pid_max-based-on-num_possible_cpus
+++ a/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(pid_max,
+ PIDS_PER_CPU_DEFAULT * num_possible_cpus()));
+ pid_max_min = max(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);
_
Patches currently in -mm which might be from travis@xxxxxxx are
linux-next.patch
pids-increase-pid_max-based-on-num_possible_cpus.patch
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