Re: [Xen-devel] [PATCH] full support of setting scheduler parameters on domain creation

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Mon, 2012-05-21 at 12:46 +0100, Juergen Gross wrote:
> Obtains current scheduler parameters before modifying any settings specified
> via domain config. Only specified settings must be modified, of course!
> 

I presume this will fix the 
libxl: error: libxl.c:3208:libxl_sched_credit_domain_set: Cpu weight out
of range, valid values are within range from 1 to 65535
warning we are currently seeing? Thanks!

> @@ -233,6 +233,14 @@ libxl_sched_params = Struct("sched_param
>      ("slice",        integer),
>      ("latency",      integer),
>      ("extratime",    integer),
> +    ("set_weight",       bool),
> +    ("set_cap",          bool),
> +    ("set_tslice_ms",    bool),
> +    ("set_ratelimit_us", bool),
> +    ("set_period",       bool),
> +    ("set_slice",        bool),
> +    ("set_latency",      bool),
> +    ("set_extratime",    bool),

Rather than doing this it would be preferable to identify some specific
value which means "default" for each of these fields. Generally this
would be either 0 (preferred if possible) or ~0 or -1. You can then
describe this in the IDL using the "init_val" property on each field.
e.g.:

@@ -225,7 +225,7 @@ libxl_domain_create_info = Struct("domai
 MemKB = UInt(64, init_val = "LIBXL_MEMKB_DEFAULT")
 
 libxl_sched_params = Struct("sched_params",[
-    ("weight",       integer),
+    ("weight",       integer, {'init_val': -1}),
     ("cap",          integer),
     ("tslice_ms",    integer),
     ("ratelimit_us", integer),

(just as an illustration of a non-zero default, I suspect 0 would
actually be a fine default value for weight, and 0 is the default
init_val)

Then libxl_sched_params_init, which xl must call (perhaps indirectly,
e.g. via libxl_domain_build_info_init) would set these defaults and xl
would override them from the config and libxl would only set those which
were non-default.

Ian.



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