From 20137a490f397d9c01fc9fadd83a8d198bda4477 Mon Sep 17 00:00:00 2001 From: Hugh Dickins Date: Tue, 6 Jan 2009 14:39:54 -0800 Subject: [PATCH] swapfile: swapon randomize if nonrot Swap allocation has always started from the beginning of the swap area; but if we're dealing with a solidstate swap device which can only remap blocks within limited zones, that would sooner wear out the first zone. Therefore sys_swapon() test whether blk_queue is non-rotational, and if so randomize the cluster_next starting position for allocation. If blk_queue is nonrot, note SWP_SOLIDSTATE for later use, and report it with an "SS" at the right end of the kernel's "Adding ... swap" message (so that if it's both nonrot and discardable, "SSD" will be shown there). Perhaps something should be shown in /proc/swaps (swapon -s), but we have to be more cautious before making any addition to that format. Signed-off-by: Hugh Dickins Cc: KAMEZAWA Hiroyuki Cc: Nick Piggin Cc: David Woodhouse Cc: Jens Axboe Cc: Matthew Wilcox Cc: Joern Engel Cc: James Bottomley Cc: Donjun Shin Cc: Tejun Heo Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/swap.h | 1 + mm/swapfile.c | 11 +++++++++-- 2 files changed, 10 insertions(+), 2 deletions(-) diff --git a/include/linux/swap.h b/include/linux/swap.h index fe79f44c858e..cbf7fbed3dfd 100644 --- a/include/linux/swap.h +++ b/include/linux/swap.h @@ -122,6 +122,7 @@ enum { SWP_WRITEOK = (1 << 1), /* ok to write to this swap? */ SWP_DISCARDABLE = (1 << 2), /* blkdev supports discard */ SWP_DISCARDING = (1 << 3), /* now discarding a free cluster */ + SWP_SOLIDSTATE = (1 << 4), /* blkdev seeks are cheap */ /* add others here before... */ SWP_SCANNING = (1 << 8), /* refcount in scan_swap_map */ }; diff --git a/mm/swapfile.c b/mm/swapfile.c index ca75b9e7c09f..b0f56603b9be 100644 --- a/mm/swapfile.c +++ b/mm/swapfile.c @@ -16,6 +16,7 @@ #include #include #include +#include #include #include #include @@ -1806,6 +1807,11 @@ asmlinkage long sys_swapon(const char __user * specialfile, int swap_flags) goto bad_swap; } + if (blk_queue_nonrot(bdev_get_queue(p->bdev))) { + p->flags |= SWP_SOLIDSTATE; + srandom32((u32)get_seconds()); + p->cluster_next = 1 + (random32() % p->highest_bit); + } if (discard_swap(p) == 0) p->flags |= SWP_DISCARDABLE; @@ -1822,10 +1828,11 @@ asmlinkage long sys_swapon(const char __user * specialfile, int swap_flags) total_swap_pages += nr_good_pages; printk(KERN_INFO "Adding %uk swap on %s. " - "Priority:%d extents:%d across:%lluk%s\n", + "Priority:%d extents:%d across:%lluk %s%s\n", nr_good_pages<<(PAGE_SHIFT-10), name, p->prio, nr_extents, (unsigned long long)span<<(PAGE_SHIFT-10), - (p->flags & SWP_DISCARDABLE) ? " D" : ""); + (p->flags & SWP_SOLIDSTATE) ? "SS" : "", + (p->flags & SWP_DISCARDABLE) ? "D" : ""); /* insert swap space into swap_list: */ prev = -1; -- 2.39.5