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Re: [libvirt] [PATCH V2 2/2] libxl: fix dom0 maximum memory setting




On 02/09/2017 04:58 PM, Jim Fehlig wrote:
> Joao Martins wrote:
>> On 02/08/2017 10:24 PM, Jim Fehlig wrote:
>>> When the libxl driver is initialized, it creates a virDomainDef
>>> object for dom0 and adds it to the list of domains. Total memory
>>> for dom0 was being set from the max_memkb field of libxl_dominfo
>>> struct retrieved from libxl, but this field can be set to
>>> LIBXL_MEMKB_DEFAULT (~0ULL) if dom0 maximum memory has not been
>>> explicitly set by the user.
>>>
>>> This patch adds some simple parsing of the Xen commandline,
>>> looking for a dom0_mem parameter that also specifies a 'max' value.
>>> If not specified, dom0 maximum memory is effectively all physical
>>> host memory.
>>>
>>> Signed-off-by: Jim Fehlig <jfehlig suse com>
>>
>> Argh, sorry. Failed to mention one (non-blocking) observation in the patch about
>> the parsing of "dom0_mem". Regardless,
>>
>> Acked-by: Joao Martins <joao m martins oracle com>
>>
>>> ---
>>>
>>> V2: Check return value of libxl_get_physinfo and
>>> libxlDriverGetDom0MaxmemConf.
>>>
>>>  src/libxl/libxl_conf.c   | 77 ++++++++++++++++++++++++++++++++++++++++++++++++
>>>  src/libxl/libxl_conf.h   |  4 +++
>>>  src/libxl/libxl_driver.c |  5 +++-
>>>  3 files changed, 85 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/src/libxl/libxl_conf.c b/src/libxl/libxl_conf.c
>>> index 28b05e1..7e30c7d 100644
>>> --- a/src/libxl/libxl_conf.c
>>> +++ b/src/libxl/libxl_conf.c
>>> @@ -34,6 +34,7 @@
>>>  #include "internal.h"
>>>  #include "virlog.h"
>>>  #include "virerror.h"
>>> +#include "c-ctype.h"
>>>  #include "datatypes.h"
>>>  #include "virconf.h"
>>>  #include "virfile.h"
>>> @@ -1533,6 +1534,82 @@ int libxlDriverConfigLoadFile(libxlDriverConfigPtr cfg,
>>>  
>>>  }
>>>  
>>> +/*
>>> + * dom0's maximum memory can be controled by the user with the 'dom0_mem' Xen
>>> + * command line parameter. E.g. to set dom0's initial memory to 4G and max
>>> + * memory to 8G: dom0_mem=4G,max:8G
>>> + *
>>> + * If not constrained by the user, dom0 can effectively use all host memory.
>>> + * This function returns the configured maximum memory for dom0 in kilobytes,
>>> + * either the user-specified value or total physical memory as a default.
>>> + */
>>> +int
>>> +libxlDriverGetDom0MaxmemConf(libxlDriverConfigPtr cfg,
>>> +                             unsigned long long *maxmem)
>>> +{
>>> +    char **cmd_tokens = NULL;
>>> +    char **mem_tokens = NULL;
>>> +    size_t i;
>>> +    size_t j;
>>> +    libxl_physinfo physinfo;
>>> +    int ret = -1;
>>> +
>>> +    if (cfg->verInfo->commandline == NULL ||
>>> +        !(cmd_tokens = virStringSplit(cfg->verInfo->commandline, " ", 0)))
>>> +        goto physmem;
>>> +
>>> +    for (i = 0; cmd_tokens[i] != NULL; i++) {
>>> +        if (!STRPREFIX(cmd_tokens[i], "dom0_mem="))
>>> +            continue;
>>> +
>>> +        if (!(mem_tokens = virStringSplit(cmd_tokens[i], ",", 0)))
>>> +            break;
>>> +        for (j = 0; mem_tokens[j] != NULL; j++) {
>>> +            if (STRPREFIX(mem_tokens[j], "max:")) {
>>> +                char *p = mem_tokens[j] + 4;
>>> +                unsigned long long multiplier = 1;
>> Hmm, perhaps worth a comment here (or in the command at the top of the function)
>> because if the parameter doesn't have a suffix it defaults to kilobytes (as per
>> Xen command line docs).
> 
> I've added another sentence to the comment at the top of the function.
> 
>>
>>> +
>>> +                while (c_isdigit(*p))
>>> +                    p++;
>>> +                if (virStrToLong_ull(mem_tokens[j] + 4, &p, 10, maxmem) < 0)
>>> +                    break;
>>> +                if (*p) {
>>> +                    switch (*p) {
>>> +                    case 'm':
>>> +                    case 'M':
>>> +                        multiplier = 1024;
>>> +                        break;
>>> +                    case 'g':
>>> +                    case 'G':
>>> +                        multiplier = 1024 * 1024;
>>> +                        break;
>>> +                    }
>>> +                }
>>> +                *maxmem = *maxmem * multiplier;
>>> +                ret = 0;
>>> +                goto cleanup;
>> This seems to match xen's parsing of the parameter that is for "max=4GG" or
>> "max=4GM" the latter suffix will be ignored (thus considering 4G only). I was
>> looking at the Xen's code of dom0_mem parsing and it's documentation - and
>> noticed that we don't support Terabytes in the parsing above. Though this is
>> only since Xen 4.5.
> 
> Good point. I've included support for the terabyte suffix. How about the below
> diff squashed in?

Looking good indeed, and with that diff I have no further comments:

Acked-by: Joao Martins <joao m martins oracle com>

> 
> Regards,
> Jim
> 
> 
> --- a/src/libxl/libxl_conf.c
> +++ b/src/libxl/libxl_conf.c
> @@ -1564,6 +1564,8 @@ int libxlDriverConfigLoadFile(libxlDriverConfigPtr cfg,
>   * dom0's maximum memory can be controled by the user with the 'dom0_mem' Xen
>   * command line parameter. E.g. to set dom0's initial memory to 4G and max
>   * memory to 8G: dom0_mem=4G,max:8G
> + * Supported unit suffixes are [bBkKmMgGtT]. If not specified the default
> + * unit is kilobytes.
>   *
>   * If not constrained by the user, dom0 can effectively use all host memory.
>   * This function returns the configured maximum memory for dom0 in kilobytes,
> @@ -1609,6 +1611,10 @@ libxlDriverGetDom0MaxmemConf(libxlDriverConfigPtr cfg,
>                      case 'G':
>                          multiplier = 1024 * 1024;
>                          break;
> +                    case 't':
> +                    case 'T':
> +                        multiplier = 1024 * 1024 * 1024;
> +                        break;
>                      }
>                  }
>                  *maxmem = *maxmem * multiplier;
> 


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