Introduce three guiding sizes for the initial readahead method. - ra_pages0: min readahead on start-of-file - ra_thrash_bytes: estimated thrashing threshold ra_thrash_bytes defaults to large value: - most systems don't have the danger of thrashing - it increases slowly and drops rapidly Signed-off-by: Wu Fengguang Signed-off-by: Andrew Morton --- linux-2.6.19-rc5-mm2.orig/include/linux/backing-dev.h +++ linux-2.6.19-rc5-mm2/include/linux/backing-dev.h @@ -26,6 +26,8 @@ typedef int (congested_fn)(void *, int); struct backing_dev_info { unsigned long ra_pages; /* max readahead in PAGE_CACHE_SIZE units */ + unsigned long ra_pages0; /* min readahead on start of file */ + unsigned long ra_thrash_bytes; /* estimated thrashing threshold */ unsigned long state; /* Always use atomic bitops on this */ unsigned int capabilities; /* Device capabilities */ congested_fn *congested_fn; /* Function pointer if device is md/dm */ --- linux-2.6.19-rc5-mm2.orig/mm/readahead.c +++ linux-2.6.19-rc5-mm2/mm/readahead.c @@ -32,6 +32,9 @@ * Adaptive read-ahead parameters. */ +/* Default initial read-ahead size. */ +#define INITIAL_RA_PAGES DIV_ROUND_UP(64*1024, PAGE_CACHE_SIZE) + /* In laptop mode, poll delayed look-ahead on every ## pages read. */ #define LAPTOP_POLL_INTERVAL 16 @@ -114,6 +117,8 @@ EXPORT_SYMBOL(default_unplug_io_fn); struct backing_dev_info default_backing_dev_info = { .ra_pages = MAX_RA_PAGES, + .ra_pages0 = INITIAL_RA_PAGES, + .ra_thrash_bytes = MAX_RA_PAGES * PAGE_CACHE_SIZE, .state = 0, .capabilities = BDI_CAP_MAP_COPY, .unplug_io_fn = default_unplug_io_fn, --- linux-2.6.19-rc5-mm2.orig/block/ll_rw_blk.c +++ linux-2.6.19-rc5-mm2/block/ll_rw_blk.c @@ -214,9 +214,6 @@ void blk_queue_make_request(request_queu blk_queue_max_phys_segments(q, MAX_PHYS_SEGMENTS); blk_queue_max_hw_segments(q, MAX_HW_SEGMENTS); q->make_request_fn = mfn; - q->backing_dev_info.ra_pages = (VM_MAX_READAHEAD * 1024) / PAGE_CACHE_SIZE; - q->backing_dev_info.state = 0; - q->backing_dev_info.capabilities = BDI_CAP_MAP_COPY; blk_queue_max_sectors(q, SAFE_MAX_SECTORS); blk_queue_hardsect_size(q, 512); blk_queue_dma_alignment(q, 511); @@ -1848,6 +1845,7 @@ request_queue_t *blk_alloc_queue_node(gf q->kobj.ktype = &queue_ktype; kobject_init(&q->kobj); + q->backing_dev_info = default_backing_dev_info; q->backing_dev_info.unplug_io_fn = blk_backing_dev_unplug; q->backing_dev_info.unplug_io_data = q; -- - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/