Commit 72680a19 authored by Hedi Berriche's avatar Hedi Berriche Committed by Linus Torvalds
Browse files

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.

[ fix warnings]
Signed-off-by: default avatarHedi Berriche <>
Signed-off-by: default avatarMike Travis <>
Signed-off-by: default avatarRobin Holt <>
Acked-by: default avatarLinus Torvalds <>
Cc: Ingo Molnar <>
Cc: Pavel Machek <>
Cc: Alan Cox <>
Cc: Greg KH <>
Cc: Rik van Riel <>
Cc: John Stoffel <>
Cc: Jack Steiner <>
Signed-off-by: default avatarAndrew Morton <>
Signed-off-by: default avatarLinus Torvalds <>
parent bd4fb654
......@@ -33,4 +33,13 @@
(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_MIN 8
......@@ -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);
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