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optimize sysfs device and attribute cache

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Add negative cache for attributes and look for device in cache before doing
any sysfs access. (Three times speed up for a stupid 1000 rules SYSFS file).

Signed-off-by: Kay Sievers <kay.sievers@suse.de>
This commit is contained in:
Kay Sievers 2006-01-29 02:09:35 +01:00
parent 3d94fb8742
commit 34f55103c5
2 changed files with 48 additions and 29 deletions
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1
udev.h
View File

@ -54,6 +54,7 @@ struct udev_rules;
struct sysfs_device {
struct list_head node; /* for device cache */
struct sysfs_device *parent; /* already cached parent*/
char devpath[PATH_SIZE];
char subsystem[NAME_SIZE]; /* $class/$bus/"drivers" */
char kernel_name[NAME_SIZE]; /* device instance name */

76
udev_sysfs.c
View File

@ -40,7 +40,8 @@ static LIST_HEAD(attr_list);
struct sysfs_attr {
struct list_head node;
char path[PATH_SIZE];
char value[NAME_SIZE];
char *value; /* points to value_local if value is cached */
char value_local[NAME_SIZE];
};
int sysfs_init(void)
@ -126,14 +127,21 @@ struct sysfs_device *sysfs_device_get(const char *devpath)
strlcpy(devpath_real, devpath, sizeof(devpath_real));
remove_trailing_chars(devpath_real, '/');
/* look for device already in cache (we never put an untranslated path in the cache) */
list_for_each_entry(dev_loop, &dev_list, node) {
if (strcmp(dev_loop->devpath, devpath_real) == 0) {
dbg("found in cache '%s'", dev_loop->devpath);
return dev_loop;
}
}
/* if we got a link, resolve it to the real device */
strlcpy(path, sysfs_path, sizeof(path));
strlcat(path, devpath_real, sizeof(path));
if (lstat(path, &statbuf) != 0) {
dbg("stat '%s' failed: %s", path, strerror(errno));
return NULL;
}
/* if we got a link, resolve it to the real device */
if (S_ISLNK(statbuf.st_mode)) {
int i;
int back;
@ -156,17 +164,17 @@ struct sysfs_device *sysfs_device_get(const char *devpath)
dbg("after moving back '%s'", devpath_real);
strlcat(devpath_real, "/", sizeof(devpath_real));
strlcat(devpath_real, &link_target[back * 3], sizeof(devpath_real));
}
/* look for device in cache */
list_for_each_entry(dev_loop, &dev_list, node) {
if (strcmp(dev_loop->devpath, devpath_real) == 0) {
dbg("found in cache '%s'", dev_loop->devpath);
return dev_loop;
/* now look for device in cache after path translation */
list_for_each_entry(dev_loop, &dev_list, node) {
if (strcmp(dev_loop->devpath, devpath_real) == 0) {
dbg("found in cache '%s'", dev_loop->devpath);
return dev_loop;
}
}
}
/* new device */
/* it is a new device */
dbg("'%s'", devpath_real);
dev = malloc(sizeof(struct sysfs_device));
if (dev == NULL)
@ -245,6 +253,9 @@ struct sysfs_device *sysfs_device_get_parent(struct sysfs_device *dev)
int len;
int back;
if (dev->parent != NULL)
return dev->parent;
/* requesting a parent is only valid for devices */
if ((strncmp(dev->devpath, "/devices/", 9) != 0) &&
(strncmp(dev->devpath, "/class/", 7) != 0) &&
@ -266,12 +277,11 @@ struct sysfs_device *sysfs_device_get_parent(struct sysfs_device *dev)
return NULL;
}
/* at the top level we may follow the "device" link */
/* at the top level of class/block we want to follow the "device" link */
if (strcmp(parent_devpath, "/block") == 0) {
dbg("/block top level, look for device link");
goto device_link;
}
if (strncmp(parent_devpath, "/class", 6) == 0) {
pos = strrchr(parent_devpath, '/');
if (pos == &parent_devpath[6] || pos == parent_devpath) {
@ -279,7 +289,8 @@ struct sysfs_device *sysfs_device_get_parent(struct sysfs_device *dev)
goto device_link;
}
}
return sysfs_device_get(parent_devpath);
dev->parent = sysfs_device_get(parent_devpath);
return dev->parent;
device_link:
strlcpy(device_link, sysfs_path, sizeof(device_link));
@ -304,7 +315,9 @@ device_link:
dbg("after moving back '%s'", parent_devpath);
strlcat(parent_devpath, "/", sizeof(parent_devpath));
strlcat(parent_devpath, &device_link_target[back * 3], sizeof(parent_devpath));
return sysfs_device_get(parent_devpath);
dev->parent = sysfs_device_get(parent_devpath);
return dev->parent;
}
struct sysfs_device *sysfs_device_get_parent_with_subsystem(struct sysfs_device *dev, const char *subsystem)
@ -345,27 +358,32 @@ char *sysfs_attr_get_value(const char *devpath, const char *attr_name)
}
}
/* read attribute value */
fd = open(path_full, O_RDONLY);
if (fd < 0)
return NULL;
size = read(fd, value, sizeof(value));
close(fd);
if (size < 0)
return NULL;
if (size == sizeof(value))
return NULL;
value[size] = '\0';
remove_trailing_chars(value, '\n');
/* store attribute in cache */
/* store attribute in cache (also negatives are kept in cache) */
attr = malloc(sizeof(struct sysfs_attr));
if (attr == NULL)
return NULL;
memset(attr, 0x00, sizeof(struct sysfs_attr));
strlcpy(attr->path, path, sizeof(attr->path));
strlcpy(attr->value, value, sizeof(attr->value));
dbg("add to cache '%s' '%s'", attr->path, attr->value);
list_add(&attr->node, &attr_list);
/* read attribute value */
fd = open(path_full, O_RDONLY);
if (fd < 0)
goto out;
size = read(fd, value, sizeof(value));
close(fd);
if (size < 0)
goto out;
if (size == sizeof(value))
goto out;
/* got a valid value, store and return it */
value[size] = '\0';
remove_trailing_chars(value, '\n');
strlcpy(attr->value_local, value, sizeof(attr->value_local));
attr->value = attr->value_local;
out:
return attr->value;
}