lockdep: shrink held_lock structure

struct held_lock {
        u64                        prev_chain_key;       /*     0     8 */
        struct lock_class *        class;                /*     8     8 */
        long unsigned int          acquire_ip;           /*    16     8 */
        struct lockdep_map *       instance;             /*    24     8 */
        int                        irq_context;          /*    32     4 */
        int                        trylock;              /*    36     4 */
        int                        read;                 /*    40     4 */
        int                        check;                /*    44     4 */
        int                        hardirqs_off;         /*    48     4 */

        /* size: 56, cachelines: 1 */
        /* padding: 4 */
        /* last cacheline: 56 bytes */
};

struct held_lock {
        u64                        prev_chain_key;       /*     0     8 */
        long unsigned int          acquire_ip;           /*     8     8 */
        struct lockdep_map *       instance;             /*    16     8 */
        unsigned int               class_idx:11;         /*    24:21  4 */
        unsigned int               irq_context:2;        /*    24:19  4 */
        unsigned int               trylock:1;            /*    24:18  4 */
        unsigned int               read:2;               /*    24:16  4 */
        unsigned int               check:2;              /*    24:14  4 */
        unsigned int               hardirqs_off:1;       /*    24:13  4 */

        /* size: 32, cachelines: 1 */
        /* padding: 4 */
        /* bit_padding: 13 bits */
        /* last cacheline: 32 bytes */
};

[mingo@elte.hu: shrunk hlock->class too]
[peterz@infradead.org: fixup bit sizes]
Signed-off-by: Dave Jones <davej@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>

1 files changed, 9 insertions, 7 deletions

diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h
index f270ce1582ff..b49bfa8e4a5c 100644
--- a/include/linux/lockdep.h
+++ b/include/linux/lockdep.h
@@ -190,6 +190,9 @@ struct lock_chain {
         u64                             chain_key;
 };
 
+#define MAX_LOCKDEP_KEYS_BITS           11
+#define MAX_LOCKDEP_KEYS                (1UL << MAX_LOCKDEP_KEYS_BITS)
+
 struct held_lock {
         /*
          * One-way hash of the dependency chain up to this point. We
@@ -206,14 +209,13 @@ struct held_lock {
          * with zero), here we store the previous hash value:
          */
         u64                             prev_chain_key;
-        struct lock_class               *class;
         unsigned long                   acquire_ip;
         struct lockdep_map              *instance;
-
 #ifdef CONFIG_LOCK_STAT
         u64                             waittime_stamp;
         u64                             holdtime_stamp;
 #endif
+        unsigned int                    class_idx:MAX_LOCKDEP_KEYS_BITS;
         /*
          * The lock-stack is unified in that the lock chains of interrupt
          * contexts nest ontop of process context chains, but we 'separate'
@@ -227,11 +229,11 @@ struct held_lock {
          * The following field is used to detect when we cross into an
          * interrupt context:
          */
-        int                             irq_context;
-        int                             trylock;
-        int                             read;
-        int                             check;
-        int                             hardirqs_off;
+        unsigned int irq_context:2; /* bit 0 - soft, bit 1 - hard */
+        unsigned int trylock:1;
+        unsigned int read:2;        /* see lock_acquire() comment */
+        unsigned int check:2;       /* see lock_acquire() comment */
+        unsigned int hardirqs_off:1;
 };
 
 /*