[patch] epoll bits 0.30 ...

From: Davide Libenzi (davidel@xmailserver.org)
Date: Mon Nov 04 2002 - 22:44:29 EST


These are the latest few bits for epoll. Changes :

*) Some constant adjusted

*) Comments plus

*) Better hash initialization

*) Correct timeout setup

- Davide

eventpoll.c | 55 ++++++++++++++++++++++++++++++++++++++-----------------
1 files changed, 38 insertions, 17 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);

-
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This archive was generated by hypermail 2b29 : Thu Nov 07 2002 - 22:00:36 EST