Looks good to me. Below just nitpicks.
I saw Andrew already took this into mmotm so I'm not sure he or you will do
next spin but anyway, review goes. Just nitpicks and a question.
On Tue, Jan 22, 2013 at 10:29:51AM +0800, Shaohua Li wrote:
>
> When I use several fast SSD to do swap, swapper_space.tree_lock is heavily
> contended. This makes each swap partition have one address_space to reduce the
> lock contention. There is an array of address_space for swap. The swap entry
> type is the index to the array.
>
> In my test with 3 SSD, this increases the swapout throughput 20%.
>
> V1->V2: simplify code
>
> Signed-off-by: Shaohua Li <shli@xxxxxxxxxxxx>
Acked-by: Minchan Kim <minchan@xxxxxxxxxx>
> ---
> fs/proc/meminfo.c | 4 +--
> include/linux/swap.h | 9 ++++----
> mm/memcontrol.c | 4 +--
> mm/mincore.c | 5 ++--
> mm/swap.c | 9 ++++++--
> mm/swap_state.c | 57 ++++++++++++++++++++++++++++++++++-----------------
> mm/swapfile.c | 5 ++--
> mm/util.c | 10 ++++++--
> 8 files changed, 68 insertions(+), 35 deletions(-)
>
> Index: linux/include/linux/swap.h
> ===================================================================
> --- linux.orig/include/linux/swap.h 2013-01-22 09:13:14.000000000 +0800
> +++ linux/include/linux/swap.h 2013-01-22 09:34:44.923011706 +0800
> @@ -8,7 +8,7 @@
> #include <linux/memcontrol.h>
> #include <linux/sched.h>
> #include <linux/node.h>
> -
> +#include <linux/fs.h>
> #include <linux/atomic.h>
> #include <asm/page.h>
>
> @@ -330,8 +330,9 @@ int generic_swapfile_activate(struct swa
> sector_t *);
>
> /* linux/mm/swap_state.c */
> -extern struct address_space swapper_space;
> -#define total_swapcache_pages swapper_space.nrpages
> +extern struct address_space swapper_spaces[];
> +#define swap_address_space(entry) (&swapper_spaces[swp_type(entry)])
How about this naming?
#define swapper_space(entry) (&swapper_spaces[swp_type(entry)])
> +extern unsigned long total_swapcache_pages(void);
> extern void show_swap_cache_info(void);
> extern int add_to_swap(struct page *);
> extern int add_to_swap_cache(struct page *, swp_entry_t, gfp_t);
> @@ -382,7 +383,7 @@ mem_cgroup_uncharge_swapcache(struct pag
>
> #define nr_swap_pages 0L
> #define total_swap_pages 0L
> -#define total_swapcache_pages 0UL
> +#define total_swapcache_pages() 0UL
>
> #define si_swapinfo(val) \
> do { (val)->freeswap = (val)->totalswap = 0; } while (0)
> Index: linux/mm/memcontrol.c
> ===================================================================
> --- linux.orig/mm/memcontrol.c 2013-01-22 09:13:14.000000000 +0800
Acked-by: Minchan Kim <minchan@xxxxxxxxxx>
> +++ linux/mm/memcontrol.c 2013-01-22 09:29:29.374977700 +0800
> @@ -6279,7 +6279,7 @@ static struct page *mc_handle_swap_pte(s
> * Because lookup_swap_cache() updates some statistics counter,
> * we call find_get_page() with swapper_space directly.
> */
> - page = find_get_page(&swapper_space, ent.val);
> + page = find_get_page(swap_address_space(ent), ent.val);
> if (do_swap_account)
> entry->val = ent.val;
>
> @@ -6320,7 +6320,7 @@ static struct page *mc_handle_file_pte(s
> swp_entry_t swap = radix_to_swp_entry(page);
> if (do_swap_account)
> *entry = swap;
> - page = find_get_page(&swapper_space, swap.val);
> + page = find_get_page(swap_address_space(swap), swap.val);
> }
> #endif
> return page;
> Index: linux/mm/mincore.c
> ===================================================================
> --- linux.orig/mm/mincore.c 2013-01-22 09:13:14.000000000 +0800
> +++ linux/mm/mincore.c 2013-01-22 09:29:29.378977649 +0800
> @@ -75,7 +75,7 @@ static unsigned char mincore_page(struct
> /* shmem/tmpfs may return swap: account for swapcache page too. */
> if (radix_tree_exceptional_entry(page)) {
> swp_entry_t swap = radix_to_swp_entry(page);
> - page = find_get_page(&swapper_space, swap.val);
> + page = find_get_page(swap_address_space(swap), swap.val);
> }
> #endif
> if (page) {
> @@ -135,7 +135,8 @@ static void mincore_pte_range(struct vm_
> } else {
> #ifdef CONFIG_SWAP
> pgoff = entry.val;
> - *vec = mincore_page(&swapper_space, pgoff);
> + *vec = mincore_page(swap_address_space(entry),
> + pgoff);
> #else
> WARN_ON(1);
> *vec = 1;
> Index: linux/mm/swap.c
> ===================================================================
> --- linux.orig/mm/swap.c 2013-01-22 09:13:14.000000000 +0800
> +++ linux/mm/swap.c 2013-01-22 09:29:29.378977649 +0800
> @@ -855,9 +855,14 @@ EXPORT_SYMBOL(pagevec_lookup_tag);
> void __init swap_setup(void)
> {
> unsigned long megs = totalram_pages >> (20 - PAGE_SHIFT);
> -
> #ifdef CONFIG_SWAP
> - bdi_init(swapper_space.backing_dev_info);
> + int i;
> +
> + for (i = 0; i < MAX_SWAPFILES; i++) {
> + bdi_init(swapper_spaces[i].backing_dev_info);
> + spin_lock_init(&swapper_spaces[i].tree_lock);
> + INIT_LIST_HEAD(&swapper_spaces[i].i_mmap_nonlinear);
> + }
> #endif
>
> /* Use a smaller cluster for small-memory machines */
> Index: linux/mm/swap_state.c
> ===================================================================
> --- linux.orig/mm/swap_state.c 2013-01-22 09:13:14.000000000 +0800
> +++ linux/mm/swap_state.c 2013-01-22 09:29:29.378977649 +0800
> @@ -36,12 +36,12 @@ static struct backing_dev_info swap_back
> .capabilities = BDI_CAP_NO_ACCT_AND_WRITEBACK | BDI_CAP_SWAP_BACKED,
> };
>
> -struct address_space swapper_space = {
> - .page_tree = RADIX_TREE_INIT(GFP_ATOMIC|__GFP_NOWARN),
> - .tree_lock = __SPIN_LOCK_UNLOCKED(swapper_space.tree_lock),
> - .a_ops = &swap_aops,
> - .i_mmap_nonlinear = LIST_HEAD_INIT(swapper_space.i_mmap_nonlinear),
> - .backing_dev_info = &swap_backing_dev_info,
> +struct address_space swapper_spaces[MAX_SWAPFILES] = {
> + [0 ... MAX_SWAPFILES - 1] = {
> + .page_tree = RADIX_TREE_INIT(GFP_ATOMIC|__GFP_NOWARN),
> + .a_ops = &swap_aops,
> + .backing_dev_info = &swap_backing_dev_info,
> + }
> };
>
> #define INC_CACHE_INFO(x) do { swap_cache_info.x++; } while (0)
> @@ -53,9 +53,19 @@ static struct {
> unsigned long find_total;
> } swap_cache_info;
>
> +unsigned long total_swapcache_pages(void)
> +{
> + int i;
> + unsigned long ret = 0;
> +
> + for (i = 0; i < MAX_SWAPFILES; i++)
> + ret += swapper_spaces[i].nrpages;
> + return ret;
> +}
> +
> void show_swap_cache_info(void)
> {
> - printk("%lu pages in swap cache\n", total_swapcache_pages);
> + printk("%lu pages in swap cache\n", total_swapcache_pages());
> printk("Swap cache stats: add %lu, delete %lu, find %lu/%lu\n",
> swap_cache_info.add_total, swap_cache_info.del_total,
> swap_cache_info.find_success, swap_cache_info.find_total);
> @@ -70,23 +80,26 @@ void show_swap_cache_info(void)
> static int __add_to_swap_cache(struct page *page, swp_entry_t entry)
> {
> int error;
> + struct address_space *address_space;
>
> VM_BUG_ON(!PageLocked(page));
> VM_BUG_ON(PageSwapCache(page));
> VM_BUG_ON(!PageSwapBacked(page));
>
> page_cache_get(page);
> - SetPageSwapCache(page);
> set_page_private(page, entry.val);
> + SetPageSwapCache(page);
Why did you move this line? Is there any special reason?
>
> - spin_lock_irq(&swapper_space.tree_lock);
> - error = radix_tree_insert(&swapper_space.page_tree, entry.val, page);
> + address_space = swap_address_space(entry);
> + spin_lock_irq(&address_space->tree_lock);
> + error = radix_tree_insert(&address_space->page_tree,
> + entry.val, page);
How about introducing utility functions to hold a lock from entry?
lock_swapper_space(entry);
unlock_swapper_space(entry);
--
Kind regards,
Minchan Kim
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