svn commit: r347487 - head/sys/vm
Doug Moore
dougm at FreeBSD.org
Sat May 11 10:16:44 UTC 2019
Author: dougm
Date: Sat May 11 10:16:43 2019
New Revision: 347487
URL: https://svnweb.freebsd.org/changeset/base/347487
Log:
Callers of swp_pager_getswapspace get either as many blocks as they
requested, or none, and in the latter case it is up to them to pick a
smaller request to make - which they always do by halving the failed
request. This change to swp_pager_getswapspace leaves the task of
downsizing the request to the function and not its caller. It still
does so by halving the original request.
Approved by: kib (mentor)
Differential Revision: https://reviews.freebsd.org/D20228
Modified:
head/sys/vm/swap_pager.c
Modified: head/sys/vm/swap_pager.c
==============================================================================
--- head/sys/vm/swap_pager.c Sat May 11 09:56:59 2019 (r347486)
+++ head/sys/vm/swap_pager.c Sat May 11 10:16:43 2019 (r347487)
@@ -407,7 +407,7 @@ static int swapoff_one(struct swdevt *sp, struct ucred
* Swap bitmap functions
*/
static void swp_pager_freeswapspace(daddr_t blk, daddr_t npages);
-static daddr_t swp_pager_getswapspace(int npages);
+static daddr_t swp_pager_getswapspace(int *npages, int limit);
/*
* Metadata functions
@@ -708,9 +708,10 @@ swap_pager_dealloc(vm_object_t object)
/*
* SWP_PAGER_GETSWAPSPACE() - allocate raw swap space
*
- * Allocate swap for the requested number of pages. The starting
- * swap block number (a page index) is returned or SWAPBLK_NONE
- * if the allocation failed.
+ * Allocate swap for up to the requested number of pages, and at
+ * least a minimum number of pages. The starting swap block number
+ * (a page index) is returned or SWAPBLK_NONE if the allocation
+ * failed.
*
* Also has the side effect of advising that somebody made a mistake
* when they configured swap and didn't configure enough.
@@ -720,38 +721,46 @@ swap_pager_dealloc(vm_object_t object)
* We allocate in round-robin fashion from the configured devices.
*/
static daddr_t
-swp_pager_getswapspace(int npages)
+swp_pager_getswapspace(int *io_npages, int limit)
{
daddr_t blk;
struct swdevt *sp;
- int i;
+ int npages;
blk = SWAPBLK_NONE;
+ npages = *io_npages;
mtx_lock(&sw_dev_mtx);
sp = swdevhd;
- for (i = 0; i < nswapdev; i++) {
+ while (!TAILQ_EMPTY(&swtailq)) {
if (sp == NULL)
sp = TAILQ_FIRST(&swtailq);
- if (!(sp->sw_flags & SW_CLOSING)) {
+ if ((sp->sw_flags & SW_CLOSING) == 0)
blk = blist_alloc(sp->sw_blist, npages);
- if (blk != SWAPBLK_NONE) {
- blk += sp->sw_first;
- sp->sw_used += npages;
- swap_pager_avail -= npages;
- swp_sizecheck();
- swdevhd = TAILQ_NEXT(sp, sw_list);
- goto done;
- }
- }
+ if (blk != SWAPBLK_NONE)
+ break;
sp = TAILQ_NEXT(sp, sw_list);
+ if (swdevhd == sp) {
+ if (npages <= limit)
+ break;
+ npages >>= 1;
+ }
}
- if (swap_pager_full != 2) {
- printf("swap_pager_getswapspace(%d): failed\n", npages);
- swap_pager_full = 2;
- swap_pager_almost_full = 1;
+ if (blk != SWAPBLK_NONE) {
+ *io_npages = npages;
+ blk += sp->sw_first;
+ sp->sw_used += npages;
+ swap_pager_avail -= npages;
+ swp_sizecheck();
+ swdevhd = TAILQ_NEXT(sp, sw_list);
+ } else {
+ if (swap_pager_full != 2) {
+ printf("swp_pager_getswapspace(%d): failed\n",
+ *io_npages);
+ swap_pager_full = 2;
+ swap_pager_almost_full = 1;
+ }
+ swdevhd = NULL;
}
- swdevhd = NULL;
-done:
mtx_unlock(&sw_dev_mtx);
return (blk);
}
@@ -886,35 +895,28 @@ swap_pager_freespace(vm_object_t object, vm_pindex_t s
int
swap_pager_reserve(vm_object_t object, vm_pindex_t start, vm_size_t size)
{
- int n = 0;
- daddr_t blk = SWAPBLK_NONE;
- vm_pindex_t beg = start; /* save start index */
- daddr_t addr, n_free, s_free;
+ daddr_t addr, blk, n_free, s_free;
+ int i, j, n;
swp_pager_init_freerange(&s_free, &n_free);
VM_OBJECT_WLOCK(object);
- while (size) {
- if (n == 0) {
- n = BLIST_MAX_ALLOC;
- while ((blk = swp_pager_getswapspace(n)) == SWAPBLK_NONE) {
- n >>= 1;
- if (n == 0) {
- swp_pager_meta_free(object, beg, start - beg);
- VM_OBJECT_WUNLOCK(object);
- return (-1);
- }
- }
+ for (i = 0; i < size; i += n) {
+ n = min(BLIST_MAX_ALLOC, size - i);
+ blk = swp_pager_getswapspace(&n, 1);
+ if (blk == SWAPBLK_NONE) {
+ swp_pager_meta_free(object, start, i);
+ VM_OBJECT_WUNLOCK(object);
+ return (-1);
}
- addr = swp_pager_meta_build(object, start, blk);
- if (addr != SWAPBLK_NONE)
- swp_pager_update_freerange(&s_free, &n_free, addr);
- --size;
- ++start;
- ++blk;
- --n;
+ for (j = 0; j < n; ++j) {
+ addr = swp_pager_meta_build(object,
+ start + i + j, blk + j);
+ if (addr != SWAPBLK_NONE)
+ swp_pager_update_freerange(&s_free, &n_free,
+ addr);
+ }
}
swp_pager_freeswapspace(s_free, n_free);
- swp_pager_meta_free(object, start, n);
VM_OBJECT_WUNLOCK(object);
return (0);
}
@@ -1384,18 +1386,8 @@ swap_pager_putpages(vm_object_t object, vm_page_t *ma,
n = min(BLIST_MAX_ALLOC, count - i);
n = min(n, nsw_cluster_max);
- /*
- * Get biggest block of swap we can. If we fail, fall
- * back and try to allocate a smaller block. Don't go
- * overboard trying to allocate space if it would overly
- * fragment swap.
- */
- while (
- (blk = swp_pager_getswapspace(n)) == SWAPBLK_NONE &&
- n > 4
- ) {
- n >>= 1;
- }
+ /* Get a block of swap of size up to size n. */
+ blk = swp_pager_getswapspace(&n, 4);
if (blk == SWAPBLK_NONE) {
for (j = 0; j < n; ++j)
rtvals[i+j] = VM_PAGER_FAIL;
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