[PATCH libdrm 1/6] amdgpu: stop using the hash table for fd_tab

* [PATCH libdrm 1/6] amdgpu: stop using the hash table for fd_tab
@ 2018-08-03 11:34 Christian König
       [not found] ` <20180803113458.28560-1-christian.koenig-5C7GfCeVMHo@public.gmane.org>
  0 siblings, 1 reply; 14+ messages in thread
From: Christian König @ 2018-08-03 11:34 UTC (permalink / raw)
  To: amd-gfx-PD4FTy7X32lNgt0PjOBp9y5qC8QIuHrW

We have so few devices that just walking a linked list is probably
faster.

Signed-off-by: Christian König <christian.koenig@amd.com>
---
 amdgpu/amdgpu_device.c   | 49 ++++++++++++++++--------------------------------
 amdgpu/amdgpu_internal.h |  1 +
 2 files changed, 17 insertions(+), 33 deletions(-)

diff --git a/amdgpu/amdgpu_device.c b/amdgpu/amdgpu_device.c
index d7aec6a4..38fd186d 100644
--- a/amdgpu/amdgpu_device.c
+++ b/amdgpu/amdgpu_device.c
@@ -43,10 +43,9 @@
 #include "util_math.h"
 
 #define PTR_TO_UINT(x) ((unsigned)((intptr_t)(x)))
-#define UINT_TO_PTR(x) ((void *)((intptr_t)(x)))
 
 static pthread_mutex_t fd_mutex = PTHREAD_MUTEX_INITIALIZER;
-static struct util_hash_table *fd_tab;
+static amdgpu_device_handle fd_list;
 
 static unsigned handle_hash(void *key)
 {
@@ -58,28 +57,8 @@ static int handle_compare(void *key1, void *key2)
 	return PTR_TO_UINT(key1) != PTR_TO_UINT(key2);
 }
 
-static unsigned fd_hash(void *key)
+static int fd_compare(int fd1, int fd2)
 {
-	int fd = PTR_TO_UINT(key);
-	char *name = drmGetPrimaryDeviceNameFromFd(fd);
-	unsigned result = 0;
-	char *c;
-
-	if (name == NULL)
-		return 0;
-
-	for (c = name; *c; ++c)
-		result += *c;
-
-	free(name);
-
-	return result;
-}
-
-static int fd_compare(void *key1, void *key2)
-{
-	int fd1 = PTR_TO_UINT(key1);
-	int fd2 = PTR_TO_UINT(key2);
 	char *name1 = drmGetPrimaryDeviceNameFromFd(fd1);
 	char *name2 = drmGetPrimaryDeviceNameFromFd(fd2);
 	int result;
@@ -127,16 +106,17 @@ static int amdgpu_get_auth(int fd, int *auth)
 
 static void amdgpu_device_free_internal(amdgpu_device_handle dev)
 {
+	amdgpu_device_handle *node = &fd_list;
+
 	pthread_mutex_lock(&fd_mutex);
-	util_hash_table_remove(fd_tab, UINT_TO_PTR(dev->fd));
-	if (util_hash_table_count(fd_tab) == 0) {
-		util_hash_table_destroy(fd_tab);
-		fd_tab = NULL;
-	}
+	while (*node != dev && (*node)->next)
+		node = &(*node)->next;
+	*node = (*node)->next;
+	pthread_mutex_unlock(&fd_mutex);
+
 	close(dev->fd);
 	if ((dev->flink_fd >= 0) && (dev->fd != dev->flink_fd))
 		close(dev->flink_fd);
-	pthread_mutex_unlock(&fd_mutex);
 
 	amdgpu_vamgr_deinit(&dev->vamgr_32);
 	amdgpu_vamgr_deinit(&dev->vamgr);
@@ -187,8 +167,6 @@ int amdgpu_device_initialize(int fd,
 	*device_handle = NULL;
 
 	pthread_mutex_lock(&fd_mutex);
-	if (!fd_tab)
-		fd_tab = util_hash_table_create(fd_hash, fd_compare);
 	r = amdgpu_get_auth(fd, &flag_auth);
 	if (r) {
 		fprintf(stderr, "%s: amdgpu_get_auth (1) failed (%i)\n",
@@ -196,7 +174,11 @@ int amdgpu_device_initialize(int fd,
 		pthread_mutex_unlock(&fd_mutex);
 		return r;
 	}
-	dev = util_hash_table_get(fd_tab, UINT_TO_PTR(fd));
+
+	for (dev = fd_list; dev; dev = dev->next)
+		if (fd_compare(dev->fd, fd) == 0)
+			break;
+
 	if (dev) {
 		r = amdgpu_get_auth(dev->fd, &flag_authexist);
 		if (r) {
@@ -297,7 +279,8 @@ int amdgpu_device_initialize(int fd,
 	*major_version = dev->major_version;
 	*minor_version = dev->minor_version;
 	*device_handle = dev;
-	util_hash_table_set(fd_tab, UINT_TO_PTR(dev->fd), dev);
+	dev->next = fd_list;
+	fd_list = dev;
 	pthread_mutex_unlock(&fd_mutex);
 
 	return 0;
diff --git a/amdgpu/amdgpu_internal.h b/amdgpu/amdgpu_internal.h
index 99b8ce0b..83012cab 100644
--- a/amdgpu/amdgpu_internal.h
+++ b/amdgpu/amdgpu_internal.h
@@ -65,6 +65,7 @@ struct amdgpu_va {
 
 struct amdgpu_device {
 	atomic_t refcount;
+	struct amdgpu_device *next;
 	int fd;
 	int flink_fd;
 	unsigned major_version;
-- 
2.14.1

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