From: Anton Ivanov <antiv...@cisco.com>
Obvious performance optimization - it is not necessary
to read the requests one at a time in the IRQ handler
Signed-off-by: Anton Ivanov <antiv...@cisco.com>
---
arch/um/drivers/ubd_kern.c | 29 ++++++++++++++++++++++-------
1 file changed, 22 insertions(+), 7 deletions(-)
diff --git a/arch/um/drivers/ubd_kern.c b/arch/um/drivers/ubd_kern.c
index 35ba00b..8568290 100644
--- a/arch/um/drivers/ubd_kern.c
+++ b/arch/um/drivers/ubd_kern.c
@@ -443,6 +443,8 @@ static void do_ubd_request(struct request_queue * q);
static int thread_fd = -1;
static LIST_HEAD(restart);
+static struct io_thread_req * ubd_request_list[MAX_SG];
+
/* XXX - move this inside ubd_intr. */
/* Called without dev->lock held, and only in interrupt context. */
static void ubd_handler(void)
@@ -451,21 +453,34 @@ static void ubd_handler(void)
struct ubd *ubd;
struct list_head *list, *next_ele;
unsigned long flags;
- int n;
+ int n, i;
+
+ /*
+ * obvious optimization - we do not need to read the reqs one at a time
+ * we can read all pending reqs in one interrupt and handle them in bulk
+ */
while(1){
- n = os_read_file(thread_fd, &req,
- sizeof(struct io_thread_req *));
- if(n != sizeof(req)){
+ do {
+ n = os_read_file(thread_fd, &ubd_request_list,
+ sizeof(struct io_thread_req *) * MAX_SG);
+ } while (n == -EINTR);
+ if(n < 0){
if(n == -EAGAIN)
break;
printk(KERN_ERR "spurious interrupt in ubd_handler, "
"err = %d\n", -n);
return;
+ } else if (n % sizeof(struct io_thread_req *) != 0) {
+ printk(KERN_ERR "spurious interrupt in ubd_handler, "
+ "err = %d\n", -n);
+ return;
+ }
+ for (i = 0; i < n / sizeof(struct io_thread_req *); i++) {
+ req = ubd_request_list[i];
+ blk_end_request(req->req, 0, req->length);
+ kfree(req);
}
-
- blk_end_request(req->req, 0, req->length);
- kfree(req);
}
list_for_each_safe(list, next_ele, &restart){
--
1.7.10.4
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