[Xen-changelog] [xen-unstable] Reduce AIO context allocations in blktap.

[Xen patchbot-unstable <patchbot-unstable@xxxxxxxxxxxxxxxxxxx>]

# HG changeset patch
# User akw@xxxxxxxxxxx
# Node ID 7bfd8efb4fa7d2e2f90bd21af3407cd2fd28744a
# Parent  8273f730371bfabbfa15f79a47a59ada06711aec
Reduce AIO context allocations in blktap.

Signed-off-by: Andrew Warfield <andy@xxxxxxxxxxxxx>
---
 tools/blktap/drivers/block-aio.c  |   19 ++++++++++++++-----
 tools/blktap/drivers/block-qcow.c |   19 +++++++++++++++----
 2 files changed, 29 insertions(+), 9 deletions(-)

diff -r 8273f730371b -r 7bfd8efb4fa7 tools/blktap/drivers/block-aio.c
--- a/tools/blktap/drivers/block-aio.c  Tue Aug 29 12:23:11 2006 +0100
+++ b/tools/blktap/drivers/block-aio.c  Tue Aug 29 14:34:57 2006 -0700
@@ -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, cons
        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, cons
 
        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 -r 8273f730371b -r 7bfd8efb4fa7 tools/blktap/drivers/block-qcow.c
--- a/tools/blktap/drivers/block-qcow.c Tue Aug 29 12:23:11 2006 +0100
+++ b/tools/blktap/drivers/block-qcow.c Tue Aug 29 14:34:57 2006 -0700
@@ -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_stat
         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];

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