Messages in this thread Patch in this message | | | Date | Fri, 06 Jul 2007 12:10:06 +0400 | From | Pavel Emelianov <> | Subject | [PATCH 12/16] Reference counting of pid naspaces by pids |
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Getting and putting the pid namespace in alloc_pid() and free_pid() is too slow. Instead this I get/put the namespace by the pidmaps. When the pidmap allocates its first pid the namespace is get, when the pidmap becomes empty - the namespace is put.
Although pids may live longer than their "fingerpints" in the pidmaps, this is ok to release the namespace with not yet freed struct pids, as this pid is not alive and no routines will use it.
Signed-off-by: Pavel Emelianov <xemul@openvz.org>
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pid.c | 19 +++++++++++++++---- 1 files changed, 15 insertions(+), 4 deletions(-)
diff -upr linux-2.6.22-rc4-mm2.orig/kernel/pid.c linux-2.6.22-rc4-mm2-2/kernel/pid.c --- linux-2.6.22-rc4-mm2.orig/kernel/pid.c 2007-06-14 12:14:29.000000000 +0400 +++ linux-2.6.22-rc4-mm2-2/kernel/pid.c 2007-07-04 19:00:38.000000000 +0400 @@ -89,16 +95,23 @@ static __cacheline_aligned_in_smp DEFIN static fastcall void free_pidmap(struct pid_namespace *pid_ns, int pid) { - struct pidmap *map = pid_ns->pidmap + pid / BITS_PER_PAGE; int offset = pid & BITS_PER_PAGE_MASK; + int map_id = pid / BITS_PER_PAGE; + struct pidmap *map = pid_ns->pidmap + map_id; + int free_pids; clear_bit(offset, map->page); - atomic_inc(&map->nr_free); + free_pids = atomic_inc_return(&map->nr_free); + + if (map_id == 0) + free_pids++; + if (free_pids == BITS_PER_PAGE) + put_pid_ns(pid_ns); } static int alloc_pidmap(struct pid_namespace *pid_ns) { - int i, offset, max_scan, pid, last = pid_ns->last_pid; + int i, offset, max_scan, pid, last = pid_ns->last_pid, free_pids; struct pidmap *map; pid = last + 1; @@ -126,7 +139,11 @@ static int alloc_pidmap(struct pid_names if (likely(atomic_read(&map->nr_free))) { do { if (!test_and_set_bit(offset, map->page)) { - atomic_dec(&map->nr_free); + free_pids = atomic_dec_return( + &map->nr_free); + if (free_pids == BITS_PER_PAGE - 1) + get_pid_ns(pid_ns); + pid_ns->last_pid = pid; return pid; } - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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