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[GFS2] Make glock hash locks proportional to NR_CPUS
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Make the number of locks used for hash chains in glock.c
proportional to NR_CPUS. Also move constants for the number
of hash chains into glock.c from incore.h since they are
not used outside of glock.c.

Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>
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Steven Whitehouse committed Sep 9, 2006
1 parent ff6af41 commit 087efdd
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Showing 2 changed files with 74 additions and 22 deletions.
93 changes: 74 additions & 19 deletions fs/gfs2/glock.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -53,8 +53,59 @@ typedef void (*glock_examiner) (struct gfs2_glock * gl);
static int gfs2_dump_lockstate(struct gfs2_sbd *sdp);
static int dump_glock(struct gfs2_glock *gl);

#define GFS2_GL_HASH_SHIFT 13
#define GFS2_GL_HASH_SIZE (1 << GFS2_GL_HASH_SHIFT)
#define GFS2_GL_HASH_MASK (GFS2_GL_HASH_SIZE - 1)

static struct gfs2_gl_hash_bucket gl_hash_table[GFS2_GL_HASH_SIZE];
static rwlock_t gl_hash_locks[GFS2_GL_HASH_SIZE];

/*
* Despite what you might think, the numbers below are not arbitrary :-)
* They are taken from the ipv4 routing hash code, which is well tested
* and thus should be nearly optimal. Later on we might tweek the numbers
* but for now this should be fine.
*
* The reason for putting the locks in a separate array from the list heads
* is that we can have fewer locks than list heads and save memory. We use
* the same hash function for both, but with a different hash mask.
*/
#if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK) || \
defined(CONFIG_PROVE_LOCKING)

#ifdef CONFIG_LOCKDEP
# define GL_HASH_LOCK_SZ 256
#else
# if NR_CPUS >= 32
# define GL_HASH_LOCK_SZ 4096
# elif NR_CPUS >= 16
# define GL_HASH_LOCK_SZ 2048
# elif NR_CPUS >= 8
# define GL_HASH_LOCK_SZ 1024
# elif NR_CPUS >= 4
# define GL_HASH_LOCK_SZ 512
# else
# define GL_HASH_LOCK_SZ 256
# endif
#endif

/* We never want more locks than chains */
#if GFS2_GL_HASH_SIZE < GL_HASH_LOCK_SZ
# undef GL_HASH_LOCK_SZ
# define GL_HASH_LOCK_SZ GFS2_GL_HASH_SIZE
#endif

static rwlock_t gl_hash_locks[GL_HASH_LOCK_SZ];

static inline rwlock_t *gl_lock_addr(unsigned int x)
{
return &gl_hash_locks[(x) & (GL_HASH_LOCK_SZ-1)];
}
#else /* not SMP, so no spinlocks required */
static inline rwlock_t *gl_lock_addr(x)
{
return NULL;
}
#endif

/**
* relaxed_state_ok - is a requested lock compatible with the current lock mode?
Expand Down Expand Up @@ -161,16 +212,16 @@ int gfs2_glock_put(struct gfs2_glock *gl)
{
int rv = 0;

write_lock(&gl_hash_locks[gl->gl_hash]);
write_lock(gl_lock_addr(gl->gl_hash));
if (kref_put(&gl->gl_ref, kill_glock)) {
list_del_init(&gl_hash_table[gl->gl_hash].hb_list);
write_unlock(&gl_hash_locks[gl->gl_hash]);
write_unlock(gl_lock_addr(gl->gl_hash));
BUG_ON(spin_is_locked(&gl->gl_spin));
glock_free(gl);
rv = 1;
goto out;
}
write_unlock(&gl_hash_locks[gl->gl_hash]);
write_unlock(gl_lock_addr(gl->gl_hash));
out:
return rv;
}
Expand Down Expand Up @@ -243,9 +294,9 @@ static struct gfs2_glock *gfs2_glock_find(const struct gfs2_sbd *sdp,
unsigned int hash = gl_hash(sdp, name);
struct gfs2_glock *gl;

read_lock(&gl_hash_locks[hash]);
read_lock(gl_lock_addr(hash));
gl = search_bucket(hash, sdp, name);
read_unlock(&gl_hash_locks[hash]);
read_unlock(gl_lock_addr(hash));

return gl;
}
Expand All @@ -272,9 +323,9 @@ int gfs2_glock_get(struct gfs2_sbd *sdp, u64 number,
unsigned int hash = gl_hash(sdp, &name);
int error;

read_lock(&gl_hash_locks[hash]);
read_lock(gl_lock_addr(hash));
gl = search_bucket(hash, sdp, &name);
read_unlock(&gl_hash_locks[hash]);
read_unlock(gl_lock_addr(hash));

if (gl || !create) {
*glp = gl;
Expand Down Expand Up @@ -316,15 +367,15 @@ int gfs2_glock_get(struct gfs2_sbd *sdp, u64 number,
if (error)
goto fail_aspace;

write_lock(&gl_hash_locks[hash]);
write_lock(gl_lock_addr(hash));
tmp = search_bucket(hash, sdp, &name);
if (tmp) {
write_unlock(&gl_hash_locks[hash]);
write_unlock(gl_lock_addr(hash));
glock_free(gl);
gl = tmp;
} else {
list_add_tail(&gl->gl_list, &gl_hash_table[hash].hb_list);
write_unlock(&gl_hash_locks[hash]);
write_unlock(gl_lock_addr(hash));
}

*glp = gl;
Expand Down Expand Up @@ -1879,20 +1930,20 @@ static int examine_bucket(glock_examiner examiner, struct gfs2_sbd *sdp,
memset(&plug.gl_flags, 0, sizeof(unsigned long));
set_bit(GLF_PLUG, &plug.gl_flags);

write_lock(&gl_hash_locks[hash]);
write_lock(gl_lock_addr(hash));
list_add(&plug.gl_list, &gl_hash_table[hash].hb_list);
write_unlock(&gl_hash_locks[hash]);
write_unlock(gl_lock_addr(hash));

for (;;) {
write_lock(&gl_hash_locks[hash]);
write_lock(gl_lock_addr(hash));

for (;;) {
tmp = plug.gl_list.next;

if (tmp == &gl_hash_table[hash].hb_list) {
list_del(&plug.gl_list);
entries = !list_empty(&gl_hash_table[hash].hb_list);
write_unlock(&gl_hash_locks[hash]);
write_unlock(gl_lock_addr(hash));
return entries;
}
gl = list_entry(tmp, struct gfs2_glock, gl_list);
Expand All @@ -1911,7 +1962,7 @@ static int examine_bucket(glock_examiner examiner, struct gfs2_sbd *sdp,
break;
}

write_unlock(&gl_hash_locks[hash]);
write_unlock(gl_lock_addr(hash));

examiner(gl);
}
Expand Down Expand Up @@ -2204,7 +2255,7 @@ static int gfs2_dump_lockstate(struct gfs2_sbd *sdp)

for (x = 0; x < GFS2_GL_HASH_SIZE; x++) {

read_lock(&gl_hash_locks[x]);
read_lock(gl_lock_addr(x));

list_for_each_entry(gl, &gl_hash_table[x].hb_list, gl_list) {
if (test_bit(GLF_PLUG, &gl->gl_flags))
Expand All @@ -2217,7 +2268,7 @@ static int gfs2_dump_lockstate(struct gfs2_sbd *sdp)
break;
}

read_unlock(&gl_hash_locks[x]);
read_unlock(gl_lock_addr(x));

if (error)
break;
Expand All @@ -2231,9 +2282,13 @@ int __init gfs2_glock_init(void)
{
unsigned i;
for(i = 0; i < GFS2_GL_HASH_SIZE; i++) {
rwlock_init(&gl_hash_locks[i]);
INIT_LIST_HEAD(&gl_hash_table[i].hb_list);
}
#ifdef GL_HASH_LOCK_SZ
for(i = 0; i < GL_HASH_LOCK_SZ; i++) {
rwlock_init(&gl_hash_locks[i]);
}
#endif
return 0;
}

3 changes: 0 additions & 3 deletions fs/gfs2/incore.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -448,9 +448,6 @@ enum {
SDF_NOATIME = 3,
};

#define GFS2_GL_HASH_SHIFT 13
#define GFS2_GL_HASH_SIZE (1 << GFS2_GL_HASH_SHIFT)
#define GFS2_GL_HASH_MASK (GFS2_GL_HASH_SIZE - 1)
#define GFS2_FSNAME_LEN 256

struct gfs2_sbd {
Expand Down

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