On Fri, Feb 19, 2010 at 12:23:59AM +0900, Minchan Kim wrote: > On Fri, 2010-02-12 at 12:00 +0000, Mel Gorman wrote: > > Unusuable free space index is a measure of external fragmentation that > > takes the allocation size into account. For the most part, the huge page > > size will be the size of interest but not necessarily so it is exported > > on a per-order and per-zone basis via /proc/pagetypeinfo. > > > > The index is normally calculated as a value between 0 and 1 which is > > obviously unsuitable within the kernel. Instead, the first three decimal > > places are used as a value between 0 and 1000 for an integer approximation. > > > > Signed-off-by: Mel Gorman <mel@xxxxxxxxx> > Reviewed-by: Minchan Kim <minchan.kim@xxxxxxxxx> > > There are comments at below. > It's very trivial so I don't care. > Thanks > > --- > > Documentation/filesystems/proc.txt | 10 ++++ > > mm/vmstat.c | 99 ++++++++++++++++++++++++++++++++++++ > > 2 files changed, 109 insertions(+), 0 deletions(-) > > > > diff --git a/Documentation/filesystems/proc.txt b/Documentation/filesystems/proc.txt > > index 1829dfb..0968a81 100644 > > --- a/Documentation/filesystems/proc.txt > > +++ b/Documentation/filesystems/proc.txt > > @@ -614,6 +614,10 @@ Node 0, zone DMA32, type Movable 169 152 113 91 77 > > Node 0, zone DMA32, type Reserve 1 2 2 2 2 0 1 1 1 1 0 > > Node 0, zone DMA32, type Isolate 0 0 0 0 0 0 0 0 0 0 0 > > > > +Unusable free space index at order > > +Node 0, zone DMA 0 0 0 2 6 18 34 67 99 227 485 > > +Node 0, zone DMA32 0 0 1 2 4 7 10 17 23 31 34 > > + > > Number of blocks type Unmovable Reclaimable Movable Reserve Isolate > > Node 0, zone DMA 2 0 5 1 0 > > Node 0, zone DMA32 41 6 967 2 0 > > @@ -629,6 +633,12 @@ then gives the same type of information as buddyinfo except broken down > > by migrate-type and finishes with details on how many page blocks of each > > type exist. > > > > +The unusable free space index measures how much of the available free > > +memory cannot be used to satisfy an allocation of a given size and is a > > +value between 0 and 1000. The higher the value, the more of free memory is > > +unusable and by implication, the worse the external fragmentation is. The > > +percentage of unusable free memory can be found by dividing this value by 10. > > + > > If min_free_kbytes has been tuned correctly (recommendations made by hugeadm > > from libhugetlbfs http://sourceforge.net/projects/libhugetlbfs/), one can > > make an estimate of the likely number of huge pages that can be allocated > > diff --git a/mm/vmstat.c b/mm/vmstat.c > > index 6051fba..d05d610 100644 > > --- a/mm/vmstat.c > > +++ b/mm/vmstat.c > > @@ -451,6 +451,104 @@ static int frag_show(struct seq_file *m, void *arg) > > return 0; > > } > > > > + > > +struct contig_page_info { > > + unsigned long free_pages; > > + unsigned long free_blocks_total; > > + unsigned long free_blocks_suitable; > > +}; > > + > > +/* > > + * Calculate the number of free pages in a zone, how many contiguous > > + * pages are free and how many are large enough to satisfy an allocation of > > + * the target size. Note that this function makes to attempt to estimate > > + * how many suitable free blocks there *might* be if MOVABLE pages were > > + * migrated. Calculating that is possible, but expensive and can be > > + * figured out from userspace > > + */ > > +static void fill_contig_page_info(struct zone *zone, > > + unsigned int suitable_order, > > + struct contig_page_info *info) > > +{ > > + unsigned int order; > > + > > + info->free_pages = 0; > > + info->free_blocks_total = 0; > > + info->free_blocks_suitable = 0; > > + > > + for (order = 0; order < MAX_ORDER; order++) { > > + unsigned long blocks; > > + > > + /* Count number of free blocks */ > > + blocks = zone->free_area[order].nr_free; > > + info->free_blocks_total += blocks; > > + > > + /* Count free base pages */ > > + info->free_pages += blocks << order; > > + > > + /* Count the suitable free blocks */ > > + if (order >= suitable_order) > > + info->free_blocks_suitable += blocks << > > + (order - suitable_order); > > + } > > +} > > + > > +/* > > + * Return an index indicating how much of the available free memory is > > + * unusable for an allocation of the requested size. > > + */ > > +static int unusable_free_index(struct zone *zone, > > Did you remain "zone" argument for later? > Anyway, It's trivial. > It's an oversight. I'll remove the parameter as unnecessary. It was needed in an earlier iteration. > > + unsigned int order, > > + struct contig_page_info *info) > > +{ > > + /* No free memory is interpreted as all free memory is unusable */ > > + if (info->free_pages == 0) > > + return 1000; > > + > > + /* > > + * 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; > > + > > +} > > + > > +static void pagetypeinfo_showunusable_print(struct seq_file *m, > > + pg_data_t *pgdat, struct zone *zone) > > +{ > > + unsigned int order; > > + > > + /* Alloc on stack as interrupts are disabled for zone walk */ > > contig_page_info would be larger than now? > I think it's small data now. I don't know why you comment it. > It's just out of curiosity. :) > It is small data. I don't remember why I felt the need to spell out why I didn't use kmalloc(). I'll drop the comment as it's not very helpful. > > > + struct contig_page_info info; > > + > > + seq_printf(m, "Node %4d, zone %8s %19s", > > + pgdat->node_id, > > + zone->name, " "); > > + for (order = 0; order < MAX_ORDER; ++order) { > > + fill_contig_page_info(zone, order, &info); > > + seq_printf(m, "%6d ", unusable_free_index(zone, order, &info)); > > + } > > + > > + seq_putc(m, '\n'); > > +} > > + > > +/* > > + * Display unusable free space index > > + * XXX: Could be a lot more efficient, but it's not a critical path > > + */ > > +static int pagetypeinfo_showunusable(struct seq_file *m, void *arg) > > +{ > > + pg_data_t *pgdat = (pg_data_t *)arg; > > + > > + seq_printf(m, "\nUnusable free space index at order\n"); > > + walk_zones_in_node(m, pgdat, pagetypeinfo_showunusable_print); > > + > > + return 0; > > +} > > + > > static void pagetypeinfo_showfree_print(struct seq_file *m, > > pg_data_t *pgdat, struct zone *zone) > > { > > @@ -558,6 +656,7 @@ static int pagetypeinfo_show(struct seq_file *m, void *arg) > > seq_printf(m, "Pages per block: %lu\n", pageblock_nr_pages); > > seq_putc(m, '\n'); > > pagetypeinfo_showfree(m, pgdat); > > + pagetypeinfo_showunusable(m, pgdat); > > pagetypeinfo_showblockcount(m, pgdat); > > > > return 0; > > > -- > Kind regards, > Minchan Kim > > -- 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/ . 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