[Qemu-block] [PATCH v3 1/3] qemu-options: explain disk I/O throttling options

[Stefan Hajnoczi]

The disk I/O throttling options have been listed for a long time but
never explained on the QEMU man page.

Suggested-by: Nini Gu <address@hidden>
Cc: Alberto Garcia <address@hidden>
Signed-off-by: Stefan Hajnoczi <address@hidden>
---
 qemu-options.hx | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/qemu-options.hx b/qemu-options.hx
index c85f77d..bbd1bd9 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -607,6 +607,30 @@ file sectors into the image file.
 conversion of plain zero writes by the OS to driver specific optimized
 zero write commands. You may even choose "unmap" if @var{discard} is set
 to "unmap" to allow a zero write to be converted to an UNMAP operation.
address@hidden address@hidden,address@hidden,address@hidden
+Specify bandwidth throttling limits in bytes per second, either for all request
+types or for reads or writes only.  Small values can lead to timeouts or hangs
+inside the guest.  A safe minimum for disks is 2 MB/s.
address@hidden address@hidden,address@hidden,address@hidden
+Specify bursts in bytes per second, either for all request types or for reads
+or writes only.  Bursts allow the guest I/O to spike above the limit
+temporarily.
address@hidden address@hidden,address@hidden,address@hidden
+Specify request rate limits in requests per second, either for all request
+types or for reads or writes only.
address@hidden address@hidden,address@hidden,address@hidden
+Specify bursts in requests per second, either for all request types or for 
reads
+or writes only.  Bursts allow the guest I/O to spike above the limit
+temporarily.
address@hidden address@hidden
+Let every @var{is} bytes of a request count as a new request for iops
+throttling purposes.  Use this option to prevent guests from circumventing iops
+limits by sending fewer but larger requests.
address@hidden address@hidden
+Join a throttling quota group with given name @var{g}.  All drives that are
+members of the same group are accounted for together.  Use this option to
+prevent guests from circumventing throttling limits by using many small disks
+instead of a single larger disk.
 @end table
 
 By default, the @option{cache=writeback} mode is used. It will report data
-- 
2.9.3