mm: update callers to use HASH_ZERO flag

Update dcache, inode, pid, mountpoint, and mount hash tables to use
HASH_ZERO, and remove initialization after allocations.  In case of
places where HASH_EARLY was used such as in __pv_init_lock_hash the
zeroed hash table was already assumed, because memblock zeroes the
memory.

CPU: SPARC M6, Memory: 7T
Before fix:
  Dentry cache hash table entries: 1073741824
  Inode-cache hash table entries: 536870912
  Mount-cache hash table entries: 16777216
  Mountpoint-cache hash table entries: 16777216
  ftrace: allocating 20414 entries in 40 pages
  Total time: 11.798s

After fix:
  Dentry cache hash table entries: 1073741824
  Inode-cache hash table entries: 536870912
  Mount-cache hash table entries: 16777216
  Mountpoint-cache hash table entries: 16777216
  ftrace: allocating 20414 entries in 40 pages
  Total time: 3.198s

CPU: Intel Xeon E5-2630, Memory: 2.2T:
Before fix:
  Dentry cache hash table entries: 536870912
  Inode-cache hash table entries: 268435456
  Mount-cache hash table entries: 8388608
  Mountpoint-cache hash table entries: 8388608
  CPU: Physical Processor ID: 0
  Total time: 3.245s

After fix:
  Dentry cache hash table entries: 536870912
  Inode-cache hash table entries: 268435456
  Mount-cache hash table entries: 8388608
  Mountpoint-cache hash table entries: 8388608
  CPU: Physical Processor ID: 0
  Total time: 3.244s

Link: http://lkml.kernel.org/r/1488432825-92126-4-git-send-email-pasha.tatashin@oracle.com
Signed-off-by: Pavel Tatashin <pasha.tatashin@oracle.com>
Reviewed-by: Babu Moger <babu.moger@oracle.com>
Cc: David Miller <davem@davemloft.net>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 4 insertions, 6 deletions

diff --git a/kernel/locking/qspinlock_paravirt.h b/kernel/locking/qspinlock_paravirt.h
index e6b2f7ad3e51..4ccfcaae5b89 100644
--- a/kernel/locking/qspinlock_paravirt.h
+++ b/kernel/locking/qspinlock_paravirt.h
@@ -193,7 +193,8 @@ void __init __pv_init_lock_hash(void)
          */
         pv_lock_hash = alloc_large_system_hash("PV qspinlock",
                                                sizeof(struct pv_hash_entry),
-                                               pv_hash_size, 0, HASH_EARLY,
+                                               pv_hash_size, 0,
+                                               HASH_EARLY | HASH_ZERO,
                                                &pv_lock_hash_bits, NULL,
                                                pv_hash_size, pv_hash_size);
 }
diff --git a/kernel/pid.c b/kernel/pid.c
index fd1cde1e4576..731c4e528f4e 100644
--- a/kernel/pid.c
+++ b/kernel/pid.c
@@ -575,16 +575,13 @@ struct pid *find_ge_pid(int nr, struct pid_namespace *ns)
  */
 void __init pidhash_init(void)
 {
-        unsigned int i, pidhash_size;
+        unsigned int pidhash_size;
 
         pid_hash = alloc_large_system_hash("PID", sizeof(*pid_hash), 0, 18,
-                                           HASH_EARLY | HASH_SMALL,
+                                           HASH_EARLY | HASH_SMALL | HASH_ZERO,
                                            &pidhash_shift, NULL,
                                            0, 4096);
         pidhash_size = 1U << pidhash_shift;
-
-        for (i = 0; i < pidhash_size; i++)
-                INIT_HLIST_HEAD(&pid_hash[i]);
 }
 
 void __init pidmap_init(void)