[patch] epoll bits 0.31 and epoll user space access library ...

Davide Libenzi (davidel@xmailserver.org)
Tue, 5 Nov 2002 12:32:55 -0800 (PST)


Linus, these are a few bits changes from 2.4.46 :

*) Some constant adjusted

*) Comments plus

*) Better hash initialization

*) Correct timeout setup

*) Added __KERNEL__ bypass to avoid userspace inclusion problems

A new user space access library to the epoll interface is available here :

http://www.xmailserver.org/linux-patches/nio-improve.html#sys_epoll

- Davide

fs/eventpoll.c | 55 +++++++++++++++++++++++++++++++---------------
include/linux/eventpoll.h | 14 +++++++----
2 files changed, 47 insertions, 22 deletions

diff -Nru linux-2.5.46.vanilla/fs/eventpoll.c linux-2.5.46.epoll/fs/eventpoll.c
--- linux-2.5.46.vanilla/fs/eventpoll.c Mon Nov 4 15:45:35 2002
+++ linux-2.5.46.epoll/fs/eventpoll.c Mon Nov 4 15:50:27 2002
@@ -61,8 +61,12 @@
/* Maximum storage for the eventpoll interest set */
#define EP_MAX_FDS_SIZE (1024 * 128)

-/* We don't want the hash to be smaller than this */
-#define EP_MIN_HASH_SIZE 101
+/*
+ * We don't want the hash to be smaller than this. This is basically
+ * the highest prime lower than (PAGE_SIZE / sizeof(struct list_head)).
+ */
+#define EP_MIN_HASH_SIZE 509
+
/*
* Event buffer dimension used to cache events before sending them in
* userspace with a __copy_to_user(). The event buffer is in stack,
@@ -188,6 +192,7 @@

static int ep_is_prime(int n);
+static int ep_size_hash(int hintsize);
static int ep_getfd(int *efd, struct inode **einode, struct file **efile);
static int ep_alloc_pages(char **pages, int numpages);
static int ep_free_pages(char **pages, int numpages);
@@ -252,14 +257,14 @@

-/* Report if the number is prime. Needed to correctly size the hash */
+/* Report if the number is prime. Needed to correctly size the hash */
static int ep_is_prime(int n)
{

if (n > 3) {
if (n & 1) {
int i, hn = n / 2;
-
+
for (i = 3; i < hn; i += 2)
if (!(n % i))
return 0;
@@ -296,9 +301,30 @@
}

+static int ep_size_hash(int hintsize)
+{
+ int maxsize = (EP_MAX_HPAGES - 1) * EP_HENTRY_X_PAGE;
+
+ /*
+ * Search the nearest prime number higher than "hintsize" and
+ * smaller than "maxsize".
+ */
+ for (; !ep_is_prime(hintsize); hintsize++);
+ if (hintsize < EP_MIN_HASH_SIZE)
+ hintsize = EP_MIN_HASH_SIZE;
+ else if (hintsize >= maxsize)
+ for (hintsize = maxsize - 1; !ep_is_prime(hintsize); hintsize--);
+
+ return hintsize;
+}
+
+
/*
* It opens an eventpoll file descriptor by suggesting a storage of "size"
- * file descriptors. It is the kernel part of the userspace epoll_create(2).
+ * file descriptors. The size parameter is just an hint about how to size
+ * data structures. It won't prevent the user to store more than "size"
+ * file descriptors inside the epoll interface. It is the kernel part of
+ * the userspace epoll_create(2).
*/
asmlinkage int sys_epoll_create(int size)
{
@@ -309,10 +335,8 @@
DNPRINTK(3, (KERN_INFO "[%p] eventpoll: sys_epoll_create(%d)\n",
current, size));

- /* Search the nearest prime number higher than "size" */
- for (; !ep_is_prime(size); size++);
- if (size < EP_MIN_HASH_SIZE)
- size = EP_MIN_HASH_SIZE;
+ /* Correctly size the hash */
+ size = ep_size_hash(size);

/*
* Creates all the items needed to setup an eventpoll file. That is,
@@ -567,7 +591,7 @@
eexit_2:
put_filp(file);
eexit_1:
- return error;
+ return error;
}

@@ -723,8 +747,7 @@
write_unlock_irqrestore(&eplock, flags);

/* Free hash pages */
- if (ep->nhpages > 0)
- ep_free_pages(ep->hpages, ep->nhpages);
+ ep_free_pages(ep->hpages, ep->nhpages);
}

@@ -1126,12 +1149,10 @@
wait_queue_t wait;

/*
- * Calculate the timeout by checking for the "infinite" value ( -1 )
- * and the overflow condition ( > MAX_SCHEDULE_TIMEOUT / HZ ). The
- * passed timeout is in milliseconds, that why (t * HZ) / 1000.
+ * Calculate the timeout by checking for the "infinite" value ( -1 ).
+ * The passed timeout is in milliseconds, that why (t * HZ) / 1000.
*/
- jtimeout = timeout == -1 || timeout > MAX_SCHEDULE_TIMEOUT / HZ ?
- MAX_SCHEDULE_TIMEOUT: (timeout * HZ) / 1000;
+ jtimeout = timeout == -1 ? MAX_SCHEDULE_TIMEOUT: (timeout * HZ) / 1000;

retry:
write_lock_irqsave(&ep->lock, flags);
diff -Nru linux-2.5.46.vanilla/include/linux/eventpoll.h linux-2.5.46.epoll/include/linux/eventpoll.h
--- linux-2.5.46.vanilla/include/linux/eventpoll.h Mon Nov 4 15:45:36 2002
+++ linux-2.5.46.epoll/include/linux/eventpoll.h Tue Nov 5 11:13:26 2002
@@ -14,10 +14,6 @@
#ifndef _LINUX_EVENTPOLL_H
#define _LINUX_EVENTPOLL_H

-/* Forward declarations to avoid compiler errors */
-struct file;
-struct pollfd;
-

/* Valid opcodes to issue to sys_epoll_ctl() */
#define EP_CTL_ADD 1
@@ -25,6 +21,13 @@
#define EP_CTL_MOD 3

+#ifdef __KERNEL__
+
+/* Forward declarations to avoid compiler errors */
+struct file;
+struct pollfd;
+
+
/* Kernel space functions implementing the user space "epoll" API */
asmlinkage int sys_epoll_create(int size);
asmlinkage int sys_epoll_ctl(int epfd, int op, int fd, unsigned int events);
@@ -34,6 +37,7 @@
/* Used in fs/file_table.c:__fput() to unlink files from the eventpoll interface */
void ep_notify_file_close(struct file *file);

+#endif /* #ifdef __KERNEL__ */

-#endif
+#endif /* #ifndef _LINUX_EVENTPOLL_H */

-
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