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Date: Thu, 25 Aug 2011 15:33:47 +0900
From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To: Dan Magenheimer <dan.magenheimer@...cle.com>
Cc: linux-kernel@...r.kernel.org, linux-mm@...ck.org, jeremy@...p.org,
hughd@...gle.com, ngupta@...are.org, konrad.wilk@...cle.com,
JBeulich@...ell.com, kurt.hackel@...cle.com, npiggin@...nel.dk,
akpm@...ux-foundation.org, riel@...hat.com, hannes@...xchg.org,
matthew@....cx, chris.mason@...cle.com,
sjenning@...ux.vnet.ibm.com, jackdachef@...il.com,
cyclonusj@...il.com
Subject: Re: Subject: [PATCH V7 3/4] mm: frontswap: add swap hooks and
extend try_to_unuse
On Tue, 23 Aug 2011 07:58:35 -0700
Dan Magenheimer <dan.magenheimer@...cle.com> wrote:
> From: Dan Magenheimer <dan.magenheimer@...cle.com>
> Subject: [PATCH V7 3/4] mm: frontswap: add swap hooks and extend try_to_unuse
>
> This third patch of four in the frontswap series adds hooks in the swap
> subsystem and extends try_to_unuse so that frontswap_shrink can do a
> "partial swapoff". Also, declarations for the extern-ified swap variables
> in the first patch are declared.
>
> Note that failed frontswap_map allocation is safe... failure is noted
> by lack of "FS" in the subsequent printk.
>
> [v7: rebase to 3.0-rc3]
> [v7: JBeulich@...ell.com: use new static inlines, no-ops if not config'd]
> [v6: rebase to 3.1-rc1]
> [v6: lliubbo@...il.com: use vzalloc]
> [v5: accidentally posted stale code for v4 that failed to compile :-(]
> [v4: rebase to 2.6.39]
> Signed-off-by: Dan Magenheimer <dan.magenheimer@...cle.com>
> Reviewed-by: Konrad Wilk <konrad.wilk@...cle.com>
> Acked-by: Jan Beulich <JBeulich@...ell.com>
> Acked-by: Seth Jennings <sjenning@...ux.vnet.ibm.com>
> Cc: Jeremy Fitzhardinge <jeremy@...p.org>
> Cc: Hugh Dickins <hughd@...gle.com>
> Cc: Johannes Weiner <hannes@...xchg.org>
> Cc: Nitin Gupta <ngupta@...are.org>
> Cc: Matthew Wilcox <matthew@....cx>
> Cc: Chris Mason <chris.mason@...cle.com>
> Cc: Rik Riel <riel@...hat.com>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
>
> --- linux/mm/swapfile.c 2011-08-08 08:19:26.336684746 -0600
> +++ frontswap/mm/swapfile.c 2011-08-23 08:21:15.301998803 -0600
> @@ -32,6 +32,8 @@
> #include <linux/memcontrol.h>
> #include <linux/poll.h>
> #include <linux/oom.h>
> +#include <linux/frontswap.h>
> +#include <linux/swapfile.h>
>
> #include <asm/pgtable.h>
> #include <asm/tlbflush.h>
> @@ -43,7 +45,7 @@ static bool swap_count_continued(struct
> static void free_swap_count_continuations(struct swap_info_struct *);
> static sector_t map_swap_entry(swp_entry_t, struct block_device**);
>
> -static DEFINE_SPINLOCK(swap_lock);
> +DEFINE_SPINLOCK(swap_lock);
> static unsigned int nr_swapfiles;
> long nr_swap_pages;
> long total_swap_pages;
> @@ -54,9 +56,9 @@ static const char Unused_file[] = "Unuse
> static const char Bad_offset[] = "Bad swap offset entry ";
> static const char Unused_offset[] = "Unused swap offset entry ";
>
> -static struct swap_list_t swap_list = {-1, -1};
> +struct swap_list_t swap_list = {-1, -1};
>
> -static struct swap_info_struct *swap_info[MAX_SWAPFILES];
> +struct swap_info_struct *swap_info[MAX_SWAPFILES];
>
> static DEFINE_MUTEX(swapon_mutex);
>
> @@ -557,6 +559,7 @@ static unsigned char swap_entry_free(str
> swap_list.next = p->type;
> nr_swap_pages++;
> p->inuse_pages--;
> + frontswap_flush_page(p->type, offset);
> if ((p->flags & SWP_BLKDEV) &&
> disk->fops->swap_slot_free_notify)
> disk->fops->swap_slot_free_notify(p->bdev, offset);
> @@ -1022,7 +1025,7 @@ static int unuse_mm(struct mm_struct *mm
> * Recycle to start on reaching the end, returning 0 when empty.
> */
> static unsigned int find_next_to_unuse(struct swap_info_struct *si,
> - unsigned int prev)
> + unsigned int prev, bool frontswap)
> {
> unsigned int max = si->max;
> unsigned int i = prev;
> @@ -1048,6 +1051,12 @@ static unsigned int find_next_to_unuse(s
> prev = 0;
> i = 1;
> }
> + if (frontswap) {
> + if (frontswap_test(si, i))
> + break;
> + else
> + continue;
> + }
Could you add comment ? If frontswap==true, only scan frontswap ?
> count = si->swap_map[i];
> if (count && swap_count(count) != SWAP_MAP_BAD)
> break;
> @@ -1059,8 +1068,12 @@ static unsigned int find_next_to_unuse(s
> * We completely avoid races by reading each swap page in advance,
> * and then search for the process using it. All the necessary
> * page table adjustments can then be made atomically.
> + *
> + * if the boolean frontswap is true, only unuse pages_to_unuse pages;
> + * pages_to_unuse==0 means all pages; ignored if frontswap is false
> */
> -static int try_to_unuse(unsigned int type)
> +int try_to_unuse(unsigned int type, bool frontswap,
> + unsigned long pages_to_unuse)
> {
> struct swap_info_struct *si = swap_info[type];
> struct mm_struct *start_mm;
> @@ -1093,7 +1106,7 @@ static int try_to_unuse(unsigned int typ
> * one pass through swap_map is enough, but not necessarily:
> * there are races when an instance of an entry might be missed.
> */
> - while ((i = find_next_to_unuse(si, i)) != 0) {
> + while ((i = find_next_to_unuse(si, i, frontswap)) != 0) {
> if (signal_pending(current)) {
> retval = -EINTR;
> break;
> @@ -1260,6 +1273,10 @@ static int try_to_unuse(unsigned int typ
> * interactive performance.
> */
> cond_resched();
> + if (frontswap && pages_to_unuse > 0) {
> + if (!--pages_to_unuse)
> + break;
> + }
> }
Is this a best-effort function and doesn't need to return condition
of pages_to_unuse ?
Caller of try_to_unuse(si, true....) is frontswap_shrink(). Right ?
Thanks,
-Kame
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