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

[Joerg Roedel <joro@8bytes.org>]

On Fri, Feb 20, 2009 at 09:18:42PM -0300, Marcelo Tosatti wrote:
> 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?

Yes. I am currently preparing patches to support gbpages in KVM. I think
they will be ready for submission next week.
The leak bugs were also found when I was debugging the code this week.
My test system has 5 gbpages an leaking one or two of them is _really_
bad ;)

Joerg