Re: [PATCH 3 of 3] full support of setting scheduler parameters on domain creation

[Juergen Gross <juergen.gross@ts.fujitsu.com>]

On 05/22/2012 02:30 PM, Ian Campbell wrote:
>> # HG changeset patch
>> # User Juergen Gross<juergen.gross@ts.fujitsu.com>
>> # Date 1337677423 -7200
>> # Node ID 953383741ff44d97587c2e75da79b092523d6e83
>> # Parent  19aaa30d7fdce2f1b56cb13399d603d955a61fb8
>> full support of setting scheduler parameters on domain creation
>>
>> Obtains default scheduler parameters before modifying any settings
>> specified
>> via domain config.
>>
>> Corrected an error for setting sedf parameters (setting .period
>> multiple
>> times).
>>
>> Signed-off-by: Juergen Gross<juergen.gross@ts.fujitsu.com>
>>
>> diff -r 19aaa30d7fdc -r 953383741ff4 tools/libxl/libxl.h
>> --- a/tools/libxl/libxl.h       Tue May 22 10:31:30 2012 +0200
>> +++ b/tools/libxl/libxl.h       Tue May 22 11:03:43 2012 +0200
>> @@ -605,6 +605,8 @@ int libxl_primary_console_exec(libxl_ctx
>>   /* May be called with info_r == NULL to check for domain's existance
>> */
>>   int libxl_domain_info(libxl_ctx*, libxl_dominfo *info_r,
>>                         uint32_t domid);
>> +int libxl_sched_set_defaults(libxl_ctx*, uint32_t poolid,
>> +                             libxl_sched_params *scparams);
> This interface really makes libxl_sched_params differ from all the other
> libxl structs (which have a public _init function and an internal
> setdefaults function). I'm not really sure its justified either, I was
> under the impression that you'd found that there were useful
> discriminating values?

Dario opted for this solution, so I proposed a patch implementing it.
I prefer this solution, too, as it isn't exporting scheduler internals to
the tools.

> If this function was called libxl_sched_init (replacing the
> autogenerated one) then it might be ok. Although I'm still not really
> sure what the issue is with having a discriminating value meaning
> default is, doing that keeps the _init function cheap too.

Okay, I can rename it.

>
>>   int libxl__sched_set_params(libxl__gc *gc, uint32_t domid,
>> libxl_sched_params *scparams)
>>   {
>>       libxl_ctx *ctx = libxl__gc_owner(gc);
>> -    libxl_scheduler sched;
>>       libxl_sched_sedf_domain sedf_info;
>>       libxl_sched_credit_domain credit_info;
>>       libxl_sched_credit2_domain credit2_info;
>>       int ret;
>>
>> -    sched = libxl_get_scheduler (ctx);
>> -    switch (sched) {
>> +    switch (scparams->sched) {
> What happens if scparams->sched is not the scheduler used for this
> domain? Should it either be checked or set somewhere?

The check would be the same as the original setting of scparams->sched.
Setting of the scheduler parameters will be rejected by the hypervisor if the
scheduler does not match.


Juergen

-- 
Juergen Gross                 Principal Developer Operating Systems
PDG ES&S SWE OS6                       Telephone: +49 (0) 89 3222 2967
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