On Fri, Feb 05, 2010 at 01:40:21PM -0800, David Rientjes wrote: > On Fri, 5 Feb 2010, Mel Gorman wrote: > > > > > + /* > > > > + * Index should be a value between 0 and 1. Return a value to 3 > > > > + * decimal places. > > > > + * > > > > + * 0 => no fragmentation > > > > + * 1 => high fragmentation > > > > + */ > > > > + return ((info->free_pages - (info->free_blocks_suitable << order)) * 1000) / info->free_pages; > > > > + > > > > > > This value is only for userspace consumption via /proc/pagetypeinfo, so > > > I'm wondering why it needs to be exported as an index. Other than a loss > > > of precision, wouldn't this be easier to understand (especially when > > > coupled with the free page counts already exported) if it were multipled > > > by 100 rather than 1000 and shown as a percent of _usable_ free memory at > > > each order? > > > > I find it easier to understand either way, but that's hardly a surprise. > > The 1000 is because of the loss of precision. I can make it a 100 but I > > don't think it makes much of a difference. > > > > This suggestion was coupled with the subsequent note that there is no > documentation of what "unusuable free space index" is, except by the > implementation itself. Since the value isn't used by the kernel, I think > exporting the value as a percent would be easier understood by the user > without looking up the semantics. I don't have strong feelings either > way, however. > I'm writing documentation. I'm keeping with the 1000 value because a) I like the precision and b) the fragmentation index is not related to percentages and I think having one as a percentage and the other as an index would cause confusion. Thanks -- Mel Gorman Part-time Phd Student Linux Technology Center University of Limerick IBM Dublin Software Lab -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>