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authorShehjar Tikoo <shehjart@gluster.com>2009-06-15 13:05:39 +0000
committerAnand V. Avati <avati@dev.gluster.com>2009-06-30 14:36:27 -0700
commitabfd8436df46ca46de9766d17445e2a0cc1da590 (patch)
tree439b55cfde924a785fef34a7b4412478ee434877 /libglusterfs/src
parent5b857d1bab2cc4b2874894a86684e1d50b257423 (diff)
libglusterfs: Turn fd-table O(1)
This commit reduces CPU usage of gf_fd_unused_get drastically by making it O(1) instead of O(n). Related to: http://bugs.gluster.com/cgi-bin/bugzilla3/show_bug.cgi?id=16 Signed-off-by: Anand V. Avati <avati@dev.gluster.com>
Diffstat (limited to 'libglusterfs/src')
-rw-r--r--libglusterfs/src/fd.c171
-rw-r--r--libglusterfs/src/fd.h20
2 files changed, 125 insertions, 66 deletions
diff --git a/libglusterfs/src/fd.c b/libglusterfs/src/fd.c
index fc78acc7c..cfebf1489 100644
--- a/libglusterfs/src/fd.c
+++ b/libglusterfs/src/fd.c
@@ -77,10 +77,32 @@ gf_roundup_power_of_two (uint32_t nr)
return result;
}
+static int
+gf_fd_chain_fd_entries (fdentry_t *entries, uint32_t startidx,
+ uint32_t endcount)
+{
+ uint32_t i = 0;
+
+ if (!entries)
+ return -1;
+
+ /* Chain only till the second to last entry because we want to
+ * ensure that the last entry has GF_FDTABLE_END.
+ */
+ for (i = startidx; i < (endcount - 1); i++)
+ entries[i].next_free = i + 1;
+
+ /* i has already been incremented upto the last entry. */
+ entries[i].next_free = GF_FDTABLE_END;
+
+ return 0;
+}
+
+
static uint32_t
gf_fd_fdtable_expand (fdtable_t *fdtable, uint32_t nr)
{
- fd_t **oldfds = NULL;
+ fdentry_t *oldfds = NULL;
uint32_t oldmax_fds = -1;
if (fdtable == NULL || nr < 0)
@@ -89,22 +111,30 @@ gf_fd_fdtable_expand (fdtable_t *fdtable, uint32_t nr)
return EINVAL;
}
- nr /= (1024 / sizeof (fd_t *));
+ nr /= (1024 / sizeof (fdentry_t));
nr = gf_roundup_power_of_two (nr + 1);
- nr *= (1024 / sizeof (fd_t *));
+ nr *= (1024 / sizeof (fdentry_t));
- oldfds = fdtable->fds;
+ oldfds = fdtable->fdentries;
oldmax_fds = fdtable->max_fds;
- fdtable->fds = CALLOC (nr, sizeof (fd_t *));
- ERR_ABORT (fdtable->fds);
+ fdtable->fdentries = CALLOC (nr, sizeof (fdentry_t));
+ ERR_ABORT (fdtable->fdentries);
fdtable->max_fds = nr;
if (oldfds) {
- uint32_t cpy = oldmax_fds * sizeof (fd_t *);
- memcpy (fdtable->fds, oldfds, cpy);
+ uint32_t cpy = oldmax_fds * sizeof (fdentry_t);
+ memcpy (fdtable->fdentries, oldfds, cpy);
}
+ gf_fd_chain_fd_entries (fdtable->fdentries, oldmax_fds,
+ fdtable->max_fds);
+
+ /* Now that expansion is done, we must update the fd list
+ * head pointer so that the fd allocation functions can continue
+ * using the expanded table.
+ */
+ fdtable->first_free = oldmax_fds;
FREE (oldfds);
return 0;
}
@@ -129,36 +159,36 @@ gf_fd_fdtable_alloc (void)
return fdtable;
}
-fd_t **
+fdentry_t *
__gf_fd_fdtable_get_all_fds (fdtable_t *fdtable, uint32_t *count)
{
- fd_t **fds = NULL;
+ fdentry_t *fdentries = NULL;
if (count == NULL) {
goto out;
}
- fds = fdtable->fds;
- fdtable->fds = calloc (fdtable->max_fds, sizeof (fd_t *));
+ fdentries = fdtable->fdentries;
+ fdtable->fdentries = calloc (fdtable->max_fds, sizeof (fdentry_t));
*count = fdtable->max_fds;
out:
- return fds;
+ return fdentries;
}
-fd_t **
+fdentry_t *
gf_fd_fdtable_get_all_fds (fdtable_t *fdtable, uint32_t *count)
{
- fd_t **fds = NULL;
+ fdentry_t *entries = NULL;
if (fdtable) {
pthread_mutex_lock (&fdtable->lock);
{
- fds = __gf_fd_fdtable_get_all_fds (fdtable, count);
+ entries = __gf_fd_fdtable_get_all_fds (fdtable, count);
}
pthread_mutex_unlock (&fdtable->lock);
}
- return fds;
+ return entries;
}
void
@@ -166,31 +196,31 @@ gf_fd_fdtable_destroy (fdtable_t *fdtable)
{
struct list_head list = {0, };
fd_t *fd = NULL;
- fd_t **fds = NULL;
+ fdentry_t *fdentries = NULL;
uint32_t fd_count = 0;
int32_t i = 0;
INIT_LIST_HEAD (&list);
- if (fdtable) {
- pthread_mutex_lock (&fdtable->lock);
- {
- fds = __gf_fd_fdtable_get_all_fds (fdtable, &fd_count);
- FREE (fdtable->fds);
- }
- pthread_mutex_unlock (&fdtable->lock);
+ if (!fdtable)
+ return;
- if (fds != NULL) {
- for (i = 0; i < fd_count; i++) {
- fd = fds[i];
- if (fd != NULL) {
- fd_unref (fd);
- }
- }
+ pthread_mutex_lock (&fdtable->lock);
+ {
+ fdentries = __gf_fd_fdtable_get_all_fds (fdtable, &fd_count);
+ FREE (fdtable->fdentries);
+ }
+ pthread_mutex_unlock (&fdtable->lock);
- FREE (fds);
+ if (fdentries != NULL) {
+ for (i = 0; i < fd_count; i++) {
+ fd = fdentries[i].fd;
+ if (fd != NULL) {
+ fd_unref (fd);
+ }
}
+ FREE (fdentries);
pthread_mutex_destroy (&fdtable->lock);
FREE (fdtable);
}
@@ -222,19 +252,10 @@ gf_fd_unused_get2 (fdtable_t *fdtable, fd_t *fdptr, int32_t fd)
}
}
- if (!fdtable->fds[fd])
- {
- fdtable->fds[fd] = fdptr;
- fd_ref (fdptr);
- ret = fd;
- }
- else
- {
- gf_log ("fd.c",
- GF_LOG_ERROR,
- "Cannot allocate fd %d (slot not empty in fdtable)", fd);
- }
- }
+ fdtable->fdentries[fd].fd = fdptr;
+ fd_ref (fdptr);
+ ret = fd;
+ }
err:
pthread_mutex_unlock (&fdtable->lock);
@@ -245,7 +266,10 @@ err:
int32_t
gf_fd_unused_get (fdtable_t *fdtable, fd_t *fdptr)
{
- int32_t fd = -1, i = 0;
+ int32_t fd = -1;
+ fdentry_t *fde = NULL;
+ int error;
+ int alloc_attempts = 0;
if (fdtable == NULL || fdptr == NULL)
{
@@ -255,28 +279,42 @@ gf_fd_unused_get (fdtable_t *fdtable, fd_t *fdptr)
pthread_mutex_lock (&fdtable->lock);
{
- for (i = 0; i<fdtable->max_fds; i++)
- {
- if (!fdtable->fds[i])
- break;
- }
-
- if (i < fdtable->max_fds) {
- fdtable->fds[i] = fdptr;
- fd = i;
+fd_alloc_try_again:
+ if (fdtable->first_free != GF_FDTABLE_END) {
+ fde = &fdtable->fdentries[fdtable->first_free];
+ fd = fdtable->first_free;
+ fdtable->first_free = fde->next_free;
+ fde->next_free = GF_FDENTRY_ALLOCATED;
+ fde->fd = fdptr;
} else {
- int32_t error;
- error = gf_fd_fdtable_expand (fdtable, fdtable->max_fds + 1);
+ /* If this is true, there is something
+ * seriously wrong with our data structures.
+ */
+ if (alloc_attempts >= 2) {
+ gf_log ("server-protocol.c", GF_LOG_ERROR,
+ "Multiple attempts to expand fd table"
+ " have failed.");
+ goto out;
+ }
+ error = gf_fd_fdtable_expand (fdtable,
+ fdtable->max_fds + 1);
if (error) {
gf_log ("server-protocol.c",
GF_LOG_ERROR,
"Cannot expand fdtable:%s", strerror (error));
- } else {
- fdtable->fds[i] = fdptr;
- fd = i;
+ goto out;
}
+ ++alloc_attempts;
+ /* At this point, the table stands expanded
+ * with the first_free referring to the first
+ * free entry in the new set of fdentries that
+ * have just been allocated. That means, the
+ * above logic should just work.
+ */
+ goto fd_alloc_try_again;
}
}
+out:
pthread_mutex_unlock (&fdtable->lock);
return fd;
@@ -287,6 +325,8 @@ inline void
gf_fd_put (fdtable_t *fdtable, int32_t fd)
{
fd_t *fdptr = NULL;
+ fdentry_t *fde = NULL;
+
if (fdtable == NULL || fd < 0)
{
gf_log ("fd", GF_LOG_ERROR, "invalid argument");
@@ -301,8 +341,11 @@ gf_fd_put (fdtable_t *fdtable, int32_t fd)
pthread_mutex_lock (&fdtable->lock);
{
- fdptr = fdtable->fds[fd];
- fdtable->fds[fd] = NULL;
+ fde = &fdtable->fdentries[fd];
+ fdptr = fde->fd;
+ fde->fd = NULL;
+ fde->next_free = fdtable->first_free;
+ fdtable->first_free = fd;
}
pthread_mutex_unlock (&fdtable->lock);
@@ -333,7 +376,7 @@ gf_fd_fdptr_get (fdtable_t *fdtable, int64_t fd)
pthread_mutex_lock (&fdtable->lock);
{
- fdptr = fdtable->fds[fd];
+ fdptr = fdtable->fdentries[fd].fd;
if (fdptr) {
fd_ref (fdptr);
}
diff --git a/libglusterfs/src/fd.h b/libglusterfs/src/fd.h
index d3c9afde3..b4bb12118 100644
--- a/libglusterfs/src/fd.h
+++ b/libglusterfs/src/fd.h
@@ -51,14 +51,30 @@ struct _fd {
};
typedef struct _fd fd_t;
+struct fd_table_entry {
+ fd_t *fd;
+ int next_free;
+};
+typedef struct fd_table_entry fdentry_t;
+
struct _fdtable {
int refcount;
uint32_t max_fds;
pthread_mutex_t lock;
- fd_t **fds;
+ fdentry_t *fdentries;
+ int first_free;
};
typedef struct _fdtable fdtable_t;
+/* Signifies no more entries in the fd table. */
+#define GF_FDTABLE_END -1
+
+/* The value us the same as GF_FDTABLE_END but the
+ * purpose is different here. This is used to invalidated
+ * the next_free value in an fdentry that has been allocated
+ */
+#define GF_FDENTRY_ALLOCATED -1
+
#include "logging.h"
#include "xlator.h"
@@ -77,7 +93,7 @@ gf_fd_unused_get (fdtable_t *fdtable, fd_t *fdptr);
int32_t
gf_fd_unused_get2 (fdtable_t *fdtable, fd_t *fdptr, int32_t fd);
-fd_t **
+fdentry_t *
gf_fd_fdtable_get_all_fds (fdtable_t *fdtable, uint32_t *count);
void