From: akw@devbox.site <akw@devbox.site>
Date: Tue, 29 Aug 2006 21:34:57 +0000 (-0700)
Subject: Reduce AIO context allocations in blktap.
X-Git-Tag: archive/raspbian/4.8.0-1+rpi1~1^2~15673^2~23^2~10
X-Git-Url: https://dgit.raspbian.org/%22http://www.example.com/cgi/success//%22http:/www.example.com/cgi/success/?a=commitdiff_plain;h=8c6d286668037e1eccd13ff32dd07ee1ba872591;p=xen.git

Reduce AIO context allocations in blktap.

Signed-off-by: Andrew Warfield <andy@xensource.com>
---

diff --git a/tools/blktap/drivers/block-aio.c b/tools/blktap/drivers/block-aio.c
index ebcfc35f56..48307faef5 100644
--- a/tools/blktap/drivers/block-aio.c
+++ b/tools/blktap/drivers/block-aio.c
@@ -52,7 +52,7 @@
  */
 #define REQUEST_ASYNC_FD 1
 
-#define MAX_AIO_REQS (MAX_REQUESTS * MAX_SEGMENTS_PER_REQ * 8)
+#define MAX_AIO_REQS (MAX_REQUESTS * MAX_SEGMENTS_PER_REQ)
 
 struct pending_aio {
 	td_callback_t cb;
@@ -146,7 +146,7 @@ int tdaio_open (struct td_state *s, const char *name)
 	struct tdaio_state *prv = (struct tdaio_state *)s->private;
 	s->private = prv;
 
-	DPRINTF("XXX: block-aio open('%s')", name);
+	DPRINTF("block-aio open('%s')", name);
 	/* Initialize AIO */
 	prv->iocb_free_count = MAX_AIO_REQS;
 	prv->iocb_queued     = 0;
@@ -156,9 +156,18 @@ int tdaio_open (struct td_state *s, const char *name)
 
 	if (prv->poll_fd < 0) {
 		ret = prv->poll_fd;
-		DPRINTF("Couldn't get fd for AIO poll support.  This is "
-			"probably because your kernel does not have the "
-			"aio-poll patch applied.\n");
+                if (ret == -EAGAIN) {
+                        DPRINTF("Couldn't setup AIO context.  If you are "
+                                "trying to concurrently use a large number "
+                                "of blktap-based disks, you may need to "
+                                "increase the system-wide aio request limit. "
+                                "(e.g. 'echo echo 1048576 > /proc/sys/"
+                                "aio-max-nr')\n");
+                } else {
+                        DPRINTF("Couldn't get fd for AIO poll support.  This "
+                                "is probably because your kernel does not "
+                                "have the aio-poll patch applied.\n");
+                }
 		goto done;
 	}
 
diff --git a/tools/blktap/drivers/block-qcow.c b/tools/blktap/drivers/block-qcow.c
index 7eab8c9834..d586534161 100644
--- a/tools/blktap/drivers/block-qcow.c
+++ b/tools/blktap/drivers/block-qcow.c
@@ -51,7 +51,7 @@
 /******AIO DEFINES******/
 #define REQUEST_ASYNC_FD 1
 #define MAX_QCOW_IDS  0xFFFF
-#define MAX_AIO_REQS (MAX_REQUESTS * MAX_SEGMENTS_PER_REQ * 8)
+#define MAX_AIO_REQS (MAX_REQUESTS * MAX_SEGMENTS_PER_REQ)
 
 struct pending_aio {
         td_callback_t cb;
@@ -176,10 +176,21 @@ static int init_aio_state(struct td_state *bs)
         s->aio_ctx = (io_context_t) REQUEST_ASYNC_FD;   
         s->poll_fd = io_setup(MAX_AIO_REQS, &s->aio_ctx);
 
-        if (s->poll_fd < 0) {
-                DPRINTF("Retrieving Async poll fd failed\n");
+	if (s->poll_fd < 0) {
+                if (s->poll_fd == -EAGAIN) {
+                        DPRINTF("Couldn't setup AIO context.  If you are "
+                                "trying to concurrently use a large number "
+                                "of blktap-based disks, you may need to "
+                                "increase the system-wide aio request limit. "
+                                "(e.g. 'echo echo 1048576 > /proc/sys/"
+                                "aio-max-nr')\n");
+                } else {
+                        DPRINTF("Couldn't get fd for AIO poll support.  This "
+                                "is probably because your kernel does not "
+                                "have the aio-poll patch applied.\n");
+                }
 		goto fail;
-        }
+	}
 
         for (i=0;i<MAX_AIO_REQS;i++)
                 s->iocb_free[i] = &s->iocb_list[i];