> 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. Hmmm.. /proc/pagetype have a machine unfriendly format. perhaps, some user have own ugly /proc/pagetype parser. It have a little risk to break userland ABI. I have dumb question. Why can't we use another file? > 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. I think we can treat separately internal representaion and /proc displaing style. example, load-average have fixed point internal representaion. but /proc/loadavg hide it. So, I personally like to keep this internal representation and change external representaion to 0.000-1.000 or 0.0%-100.0% range. > Signed-off-by: Mel Gorman <mel@xxxxxxxxx> > --- > 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, > + 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 > + */ I leraned math by japanese. probably then I couldn't understand what mean "3 decimal places" awhile. Simply can't we write "Index should be a value between 0 and 1000"? > + 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 */ > + 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; > -- > 1.6.5 > -- 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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