Re: [PATCH] kvm/qemu: use statfs to determine size of huge pages

[Marcelo Tosatti <mtosatti@redhat.com>]

Hi Joerg,

On Thu, Feb 19, 2009 at 04:29:36PM +0100, Joerg Roedel wrote:
> The current method of finding out the size of huge pages does not work
> reliable anymore. Current Linux supports more than one huge page size
> but /proc/meminfo only show one of the supported sizes.
> To find out the real page size used can be found by calling statfs. This
> patch changes kvm/qemu to use statfs instead of parsing /proc/meminfo.
> 
> Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>

> +    if (fs.f_type != HUGETLBFS_MAGIC) {
> +	    fprintf(stderr, "Path not on HugeTLBFS: %s\n", path);
> +	    return 0;
>      }

Would be nicer to use standard page size (sysconf) in case its not a
hugetlbfs mount, instead of failing. Useful for testing with shmem.

> -    size = strstr(buf, needle);
> -    if (!size)
> -	return 0;
> -    size += strlen(needle);
> -    hugepagesize = strtol(size, NULL, 0);
> -    return hugepagesize;
> +    return fs.f_bsize;
>  }
>  
>  static void *alloc_mem_area(size_t memory, unsigned long *len, const char *path)
> @@ -4762,7 +4760,7 @@ static void *alloc_mem_area(size_t memory, unsigned long *len, const char *path)
>      if (asprintf(&filename, "%s/kvm.XXXXXX", path) == -1)
>  	return NULL;
>  
> -    hpagesize = gethugepagesize() * 1024;
> +    hpagesize = gethugepagesize(path);
>      if (!hpagesize)
>  	return NULL;

Out of curiosity, your immediate reason for this patch is use of
gbpages?