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Index: sys/kern/subr_blist.c
===================================================================
--- sys/kern/subr_blist.c
+++ sys/kern/subr_blist.c
@@ -295,7 +295,7 @@
* not be allocated.
*/
daddr_t
-blist_alloc(blist_t bl, int *count, int maxcount)
+blist_alloc(blist_t bl, daddr_t *io_cursor, int *count, int maxcount)
{
daddr_t blk, cursor;
@@ -310,14 +310,14 @@
* non-zero. When the cursor is zero, an allocation failure will
* stop further iterations.
*/
- for (cursor = bl->bl_cursor;; cursor = 0) {
+ for (cursor = *io_cursor;; cursor = 0) {
blk = blst_meta_alloc(bl->bl_root, cursor, count, maxcount,
bl->bl_radix);
if (blk != SWAPBLK_NONE) {
bl->bl_avail -= *count;
- bl->bl_cursor = blk + *count;
- if (bl->bl_cursor == bl->bl_blocks)
- bl->bl_cursor = 0;
+ *io_cursor = blk + *count;
+ if (*io_cursor == bl->bl_blocks)
+ *io_cursor = 0;
return (blk);
}
if (cursor == 0)
@@ -404,8 +404,7 @@
void
blist_print(blist_t bl)
{
- printf("BLIST avail = %jd, cursor = %08jx {\n",
- (uintmax_t)bl->bl_avail, (uintmax_t)bl->bl_cursor);
+ printf("BLIST avail = %jd {\n", (uintmax_t)bl->bl_avail);
if (bl->bl_root->bm_bitmap != 0)
blst_radix_print(bl->bl_root, 0, bl->bl_radix, 4);
Index: sys/sys/blist.h
===================================================================
--- sys/sys/blist.h
+++ sys/sys/blist.h
@@ -81,7 +81,6 @@
daddr_t bl_blocks; /* area of coverage */
daddr_t bl_avail; /* # available blocks */
u_daddr_t bl_radix; /* coverage radix */
- daddr_t bl_cursor; /* next-fit search starts at */
blmeta_t bl_root[1]; /* root of radix tree */
} *blist_t;
@@ -92,7 +91,7 @@
struct sbuf;
-daddr_t blist_alloc(blist_t blist, int *count, int maxcount);
+daddr_t blist_alloc(blist_t blist, daddr_t *cursor, int *count, int maxcount);
daddr_t blist_avail(blist_t blist);
blist_t blist_create(daddr_t blocks, int flags);
void blist_destroy(blist_t blist);
Index: sys/vm/swap_pager.h
===================================================================
--- sys/vm/swap_pager.h
+++ sys/vm/swap_pager.h
@@ -65,6 +65,8 @@
swblk_t sw_first;
swblk_t sw_end;
struct blist *sw_blist;
+ daddr_t sw_cursor; /* next-fit search starts at */
+ daddr_t sw_trimmer; /* where to look for free space to trim */
TAILQ_ENTRY(swdevt) sw_list;
sw_strategy_t *sw_strategy;
sw_close_t *sw_close;
Index: sys/vm/swap_pager.c
===================================================================
--- sys/vm/swap_pager.c
+++ sys/vm/swap_pager.c
@@ -737,7 +737,8 @@
if (sp == NULL)
sp = TAILQ_FIRST(&swtailq);
if ((sp->sw_flags & SW_CLOSING) == 0)
- blk = blist_alloc(sp->sw_blist, &npages, mpages);
+ blk = blist_alloc(sp->sw_blist, &sp->sw_cursor,
+ &npages, mpages);
if (blk != SWAPBLK_NONE)
break;
sp = TAILQ_NEXT(sp, sw_list);
@@ -800,7 +801,126 @@
}
+static void
+swp_pager_async_trimdone(struct buf *bp)
+{
+ struct swdevt *sp;
+ daddr_t blk;
+ int npages;
+
+ sp = (struct swdevt *)bp->b_fsprivate1;
+ blk = bp->b_blkno;
+ npages = bp->b_npages;
+ uma_zfree(swwbuf_zone, bp);
+
+ mtx_lock(&swbuf_mtx);
+ if (++nsw_wcount_async == 1)
+ wakeup(&nsw_wcount_async);
+ mtx_unlock(&swbuf_mtx);
+
+ mtx_lock(&sw_dev_mtx);
+ blk -= sp->sw_first;
+ blist_free(sp->sw_blist, blk, npages);
+ mtx_unlock(&sw_dev_mtx);
+}
+
+static int trimzone_numer = 1;
+static int trimzone_denom = 8;
+static int min_trim_alloc = 1;
+static int max_trim_alloc = 32768;
/*
+ * The 'trim zone' is the small range of addresses just ahead of the cursor
+ * likely to be allocated soon. When the trimmer falls into the trim zone,
+ * we allocate blocks with the trimmer.
+ */
+static bool
+swapdev_in_trim_zone(daddr_t start, daddr_t end, daddr_t nblks)
+{
+ return ((end + nblks - start) % nblks / trimzone_numer <
+ nblks / trimzone_denom);
+}
+
+
+/* sw_dev_mtx lock is held. */
+
+static struct buf *
+swapdev_trim(struct swdevt *sp)
+{
+ struct buf *bp;
+ daddr_t blk;
+ u_long nblks;
+ int npages;
+
+ /* Quit if the cursor is too far behind the trimmer. */
+ nblks = sp->sw_nblks;
+ if (!swapdev_in_trim_zone(sp->sw_cursor, sp->sw_trimmer, nblks))
+ return (NULL);
+
+ /* Grab a (hopefully) lot of free space allocated long ago. */
+ npages = min_trim_alloc;
+ blk = blist_alloc(sp->sw_blist, &sp->sw_trimmer,
+ &npages, max_trim_alloc);
+
+ /* Quit if there's nothing free. */
+ if (blk == SWAPBLK_NONE)
+ return (NULL);
+ if (swapdev_in_trim_zone(sp->sw_cursor, sp->sw_trimmer, nblks)) {
+ /*
+ * Trim allocation is too close to the cursor. Either we've
+ * wrapped around and jumped the cursor, or we've found too
+ * little free space close to the cursor to move the trimmer
+ * out of the trim zone. Bail out.
+ *
+ */
+ blist_free(sp->sw_blist, blk, npages);
+ return (NULL);
+ }
+ blk += sp->sw_first;
+ mtx_unlock(&sw_dev_mtx);
+ CTR3(KTR_SPARE5, "swapdev_trim: cursor %p trimmer %p trimsize %d",
+ (void*)sp->sw_cursor, (void*)sp->sw_trimmer, npages);
+ mtx_lock(&swbuf_mtx);
+ while (nsw_wcount_async == 0)
+ msleep(&nsw_wcount_async, &swbuf_mtx, PVM,
+ "swbufa", 0);
+ nsw_wcount_async--;
+ mtx_unlock(&swbuf_mtx);
+ bp = uma_zalloc(swwbuf_zone, M_WAITOK);
+ bp->b_flags = B_ASYNC;
+ bp->b_data = NULL;
+ bp->b_iocmd = BIO_DELETE;
+ bp->b_rcred = crhold(thread0.td_ucred);
+ bp->b_wcred = crhold(thread0.td_ucred);
+ bp->b_bcount = PAGE_SIZE * npages;
+ bp->b_bufsize = PAGE_SIZE * npages;
+ bp->b_blkno = blk;
+ bp->b_npages = npages;
+ bp->b_iodone = swp_pager_async_trimdone;
+ bp->b_fsprivate1 = sp;
+ BUF_KERNPROC(bp);
+ return (bp);
+}
+
+/* find a swap device that needs trimming, and start trimming */
+static void
+swp_pager_trimswapspace(void)
+{
+ struct swdevt *sp;
+ struct buf *bp;
+
+ mtx_lock(&sw_dev_mtx);
+ TAILQ_FOREACH(sp, &swtailq, sw_list) {
+ bp = swapdev_trim(sp);
+ if (bp == NULL)
+ continue;
+ /* sw_dev_mtx released in swapdev_trim */
+ sp->sw_strategy(bp,sp);
+ return;
+ }
+ mtx_unlock(&sw_dev_mtx);
+}
+
+/*
* SWP_PAGER_FREESWAPSPACE() - free raw swap space
*
* This routine returns the specified swap blocks back to the bitmap.
@@ -921,6 +1041,7 @@
}
swp_pager_freeswapspace(s_free, n_free);
VM_OBJECT_WUNLOCK(object);
+ swp_pager_trimswapspace();
return (0);
}
@@ -1388,6 +1509,7 @@
/* Get a block of swap of size up to size n. */
blk = swp_pager_getswapspace(&n, 4);
+ swp_pager_trimswapspace();
if (blk == SWAPBLK_NONE) {
for (j = 0; j < n; ++j)
rtvals[i+j] = VM_PAGER_FAIL;
@@ -2310,6 +2432,8 @@
sp->sw_flags = flags;
sp->sw_blist = blist_create(nblks, M_WAITOK);
+ sp->sw_cursor = 0;
+ sp->sw_trimmer = 0;
/*
* Do not free the first two block in order to avoid overwriting
* any bsd label at the front of the partition

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