[Qemu-devel] [PATCH v4 2/2] block: disable I/O throttling on sync api

[Qemu-devel] [PATCH v4 2/2] block: disable I/O throttling on sync api

[zwu.kernel]

From: Zhi Yong Wu <wuzhy@linux.vnet.ibm.com>

Signed-off-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
Signed-off-by: Zhi Yong Wu <wuzhy@linux.vnet.ibm.com>
---
 block.c |   20 ++++++++++++++++++++
 1 files changed, 20 insertions(+), 0 deletions(-)

diff --git a/block.c b/block.c
index 1fbf4dd..058ef17 100644
--- a/block.c
+++ b/block.c
@@ -1477,6 +1477,17 @@ static int bdrv_rw_co(BlockDriverState *bs, int64_t sector_num, uint8_t *buf,
 
     qemu_iovec_init_external(&qiov, &iov, 1);
 
+    /**
+     * In sync call context, when the vcpu is blocked, this throttling timer
+     * will not fire; so the I/O throttling function has to be disabled here
+     * if it has been enabled.
+     */
+    if (bs->io_limits_enabled) {
+        fprintf(stderr, "Disabling I/O throttling on '%s' due "
+                        "to synchronous I/O.\n", bdrv_get_device_name(bs));
+        bdrv_io_limits_disable(bs);
+    }
+
     if (qemu_in_coroutine()) {
         /* Fast-path if already in coroutine context */
         bdrv_rw_co_entry(&rwco);
@@ -1983,10 +1994,19 @@ static int guess_disk_lchs(BlockDriverState *bs,
     struct partition *p;
     uint32_t nr_sects;
     uint64_t nb_sectors;
+    bool enabled;
 
     bdrv_get_geometry(bs, &nb_sectors);
 
+    /**
+     * The function will be invoked during startup not only in sync I/O mode,
+     * but also in async I/O mode. So the I/O throttling function has to
+     * be disabled temporarily here, not permanently.
+     */
+    enabled = bs->io_limits_enabled;
+    bs->io_limits_enabled = false;
     ret = bdrv_read(bs, 0, buf, 1);
+    bs->io_limits_enabled = enabled;
     if (ret < 0)
         return -1;
     /* test msdos magic */
-- 
1.7.6

Re: [Qemu-devel] [PATCH v4 2/2] block: disable I/O throttling on sync api

[Stefan Hajnoczi]

On Mon, Apr 02, 2012 at 06:59:34PM +0800, zwu.kernel@gmail.com wrote:
> From: Zhi Yong Wu <wuzhy@linux.vnet.ibm.com>
> 
> Signed-off-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
> Signed-off-by: Zhi Yong Wu <wuzhy@linux.vnet.ibm.com>
> ---
>  block.c |   20 ++++++++++++++++++++
>  1 files changed, 20 insertions(+), 0 deletions(-)

Reviewed-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>

In the future please send the entire patch series when you publish a new
version.  This makes it easy for reviewers and maintainers to find the
latest version of your patches.

Stefan

Re: [Qemu-devel] [PATCH v4 2/2] block: disable I/O throttling on sync api

[Kevin Wolf]

Am 02.04.2012 13:48, schrieb Stefan Hajnoczi:
> On Mon, Apr 02, 2012 at 06:59:34PM +0800, zwu.kernel@gmail.com wrote:
>> From: Zhi Yong Wu <wuzhy@linux.vnet.ibm.com>
>>
>> Signed-off-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
>> Signed-off-by: Zhi Yong Wu <wuzhy@linux.vnet.ibm.com>
>> ---
>>  block.c |   20 ++++++++++++++++++++
>>  1 files changed, 20 insertions(+), 0 deletions(-)
> 
> Reviewed-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>

Thanks, applied.

> In the future please send the entire patch series when you publish a new
> version.  This makes it easy for reviewers and maintainers to find the
> latest version of your patches.

I'm assuming that this patch makes sense on its own. I'll pick up the
other one when I get to the old thread.

Kevin