git: d0b225d16418 - main - swap_pager: use iterators in swp_pager_meta_build
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Date: Tue, 08 Oct 2024 08:33:14 UTC
The branch main has been updated by dougm:
URL: https://cgit.FreeBSD.org/src/commit/?id=d0b225d16418e224b5d30d13f45515aa70ad47a3
commit d0b225d16418e224b5d30d13f45515aa70ad47a3
Author: Doug Moore <dougm@FreeBSD.org>
AuthorDate: 2024-10-08 08:31:16 +0000
Commit: Doug Moore <dougm@FreeBSD.org>
CommitDate: 2024-10-08 08:31:16 +0000
swap_pager: use iterators in swp_pager_meta_build
Add a method to use an iterator for pctrie insertion; this should
improve performance when the last search ended near the place where
the new item will be inserted.
Add an iterator argument to swp_pager_meta_build, so that the lookups
and insertions it does can be faster in the common case when keys are
bunched close together, or appear in sequence.
Reviewed by: alc
Differential Revision: https://reviews.freebsd.org/D46848
---
sys/kern/subr_pctrie.c | 36 +++++++++++++++++
sys/sys/pctrie.h | 20 +++++++++
sys/vm/swap_pager.c | 107 ++++++++++++++++++++++++++++++++-----------------
3 files changed, 126 insertions(+), 37 deletions(-)
diff --git a/sys/kern/subr_pctrie.c b/sys/kern/subr_pctrie.c
index a7b487166054..50216287845f 100644
--- a/sys/kern/subr_pctrie.c
+++ b/sys/kern/subr_pctrie.c
@@ -594,6 +594,42 @@ pctrie_iter_lookup(struct pctrie_iter *it, uint64_t index)
return (_pctrie_iter_lookup(it, index, NULL, PCTRIE_LOCKED));
}
+/*
+ * Insert the val in the trie, starting search with iterator. Return a pointer
+ * to indicate where a new node must be allocated to complete insertion.
+ * Assumes access is externally synchronized by a lock.
+ */
+void *
+pctrie_iter_insert_lookup(struct pctrie_iter *it, uint64_t *val)
+{
+ struct pctrie_node *node;
+
+ it->index = *val;
+ node = _pctrie_iter_lookup_node(it, *val, NULL, PCTRIE_LOCKED);
+ if (node == PCTRIE_NULL) {
+ if (it->top == 0)
+ pctrie_root_store(it->ptree,
+ pctrie_toleaf(val), PCTRIE_LOCKED);
+ else
+ pctrie_addnode(it->path[it->top - 1], it->index,
+ pctrie_toleaf(val), PCTRIE_LOCKED);
+ return (NULL);
+ }
+ if (__predict_false(pctrie_match_value(node, it->index) != NULL))
+ panic("%s: key %jx is already present", __func__,
+ (uintmax_t)it->index);
+
+ /*
+ * 'node' must be replaced in the tree with a new branch node, with
+ * children 'node' and 'val'. Return the place that points to 'node'
+ * now, and will point to to the new branching node later.
+ */
+ if (it->top == 0)
+ return ((smr_pctnode_t *)&it->ptree->pt_root);
+ node = it->path[it->top - 1];
+ return (&node->pn_child[pctrie_slot(node, it->index)]);
+}
+
/*
* Returns the value stored at a fixed offset from the current index value,
* possibly NULL.
diff --git a/sys/sys/pctrie.h b/sys/sys/pctrie.h
index 4d5450c25079..d71290c8cf23 100644
--- a/sys/sys/pctrie.h
+++ b/sys/sys/pctrie.h
@@ -239,6 +239,24 @@ name##_PCTRIE_RECLAIM_CALLBACK(struct pctrie *ptree, \
freefn(ptree, freenode); \
} \
\
+static __inline __unused int \
+name##_PCTRIE_ITER_INSERT(struct pctrie_iter *it, struct type *ptr) \
+{ \
+ struct pctrie_node *parent; \
+ void *parentp; \
+ uint64_t *val = name##_PCTRIE_PTR2VAL(ptr); \
+ \
+ parentp = pctrie_iter_insert_lookup(it, val); \
+ if (parentp == NULL) \
+ return (0); \
+ parent = allocfn(it->ptree); \
+ if (__predict_false(parent == NULL)) \
+ return (ENOMEM); \
+ pctrie_insert_node(parentp, parent, val); \
+ it->path[it->top++] = parent; \
+ return (0); \
+} \
+ \
static __inline __unused struct type * \
name##_PCTRIE_ITER_LOOKUP(struct pctrie_iter *it, uint64_t index) \
{ \
@@ -369,6 +387,8 @@ uint64_t *pctrie_iter_lookup(struct pctrie_iter *it, uint64_t index);
uint64_t *pctrie_iter_stride(struct pctrie_iter *it, int stride);
uint64_t *pctrie_iter_next(struct pctrie_iter *it);
uint64_t *pctrie_iter_prev(struct pctrie_iter *it);
+void *pctrie_iter_insert_lookup(struct pctrie_iter *it,
+ uint64_t *val);
uint64_t *pctrie_lookup_ge(struct pctrie *ptree, uint64_t key);
uint64_t *pctrie_subtree_lookup_gt(struct pctrie_node *node,
uint64_t key);
diff --git a/sys/vm/swap_pager.c b/sys/vm/swap_pager.c
index 807215647a93..f4db46a32dee 100644
--- a/sys/vm/swap_pager.c
+++ b/sys/vm/swap_pager.c
@@ -486,8 +486,8 @@ static daddr_t swp_pager_getswapspace(int *npages);
/*
* Metadata functions
*/
-static daddr_t swp_pager_meta_build(vm_object_t, vm_pindex_t, daddr_t,
- bool);
+static daddr_t swp_pager_meta_build(struct pctrie_iter *, vm_object_t object,
+ vm_pindex_t, daddr_t, bool);
static void swp_pager_meta_free(vm_object_t, vm_pindex_t, vm_pindex_t,
vm_size_t *);
static void swp_pager_meta_transfer(vm_object_t src, vm_object_t dst,
@@ -551,29 +551,39 @@ swblk_lookup_remove(vm_object_t object, struct swblk *sb)
SWAP_PCTRIE_REMOVE(&object->un_pager.swp.swp_blks, sb->p);
}
-static int
-swblk_lookup_insert(vm_object_t object, struct swblk *sb)
-{
- return (SWAP_PCTRIE_INSERT(&object->un_pager.swp.swp_blks, sb));
-}
-
static bool
swblk_is_empty(vm_object_t object)
{
return (pctrie_is_empty(&object->un_pager.swp.swp_blks));
}
-static struct swblk *
-swblk_iter_init(struct pctrie_iter *blks, vm_object_t object,
- vm_pindex_t pindex)
+static void
+swblk_iter_init_only(struct pctrie_iter *blks, vm_object_t object)
{
VM_OBJECT_ASSERT_LOCKED(object);
MPASS((object->flags & OBJ_SWAP) != 0);
pctrie_iter_init(blks, &object->un_pager.swp.swp_blks);
+}
+
+
+static struct swblk *
+swblk_iter_init(struct pctrie_iter *blks, vm_object_t object,
+ vm_pindex_t pindex)
+{
+ swblk_iter_init_only(blks, object);
return (SWAP_PCTRIE_ITER_LOOKUP_GE(blks,
rounddown(pindex, SWAP_META_PAGES)));
}
+static struct swblk *
+swblk_iter_reinit(struct pctrie_iter *blks, vm_object_t object,
+ vm_pindex_t pindex)
+{
+ swblk_iter_init_only(blks, object);
+ return (SWAP_PCTRIE_ITER_LOOKUP(blks,
+ rounddown(pindex, SWAP_META_PAGES)));
+}
+
static struct swblk *
swblk_iter_limit_init(struct pctrie_iter *blks, vm_object_t object,
vm_pindex_t pindex, vm_pindex_t limit)
@@ -591,6 +601,19 @@ swblk_iter_next(struct pctrie_iter *blks)
return (SWAP_PCTRIE_ITER_JUMP_GE(blks, SWAP_META_PAGES));
}
+static struct swblk *
+swblk_iter_lookup(struct pctrie_iter *blks, vm_pindex_t pindex)
+{
+ return (SWAP_PCTRIE_ITER_LOOKUP(blks,
+ rounddown(pindex, SWAP_META_PAGES)));
+}
+
+static int
+swblk_iter_insert(struct pctrie_iter *blks, struct swblk *sb)
+{
+ return (SWAP_PCTRIE_ITER_INSERT(blks, sb));
+}
+
static void
swblk_iter_remove(struct pctrie_iter *blks)
{
@@ -1081,6 +1104,7 @@ swap_pager_freespace_pgo(vm_object_t object, vm_pindex_t start, vm_size_t size)
int
swap_pager_reserve(vm_object_t object, vm_pindex_t start, vm_pindex_t size)
{
+ struct pctrie_iter blks;
struct page_range range;
daddr_t addr, blk;
vm_pindex_t i, j;
@@ -1088,6 +1112,7 @@ swap_pager_reserve(vm_object_t object, vm_pindex_t start, vm_pindex_t size)
swp_pager_init_freerange(&range);
VM_OBJECT_WLOCK(object);
+ swblk_iter_init_only(&blks, object);
for (i = 0; i < size; i += n) {
n = MIN(size - i, INT_MAX);
blk = swp_pager_getswapspace(&n);
@@ -1097,7 +1122,7 @@ swap_pager_reserve(vm_object_t object, vm_pindex_t start, vm_pindex_t size)
return (-1);
}
for (j = 0; j < n; ++j) {
- addr = swp_pager_meta_build(object,
+ addr = swp_pager_meta_build(&blks, object,
start + i + j, blk + j, false);
if (addr != SWAPBLK_NONE)
swp_pager_update_freerange(&range, addr);
@@ -1535,6 +1560,7 @@ static void
swap_pager_putpages(vm_object_t object, vm_page_t *ma, int count,
int flags, int *rtvals)
{
+ struct pctrie_iter blks;
struct page_range range;
struct buf *bp;
daddr_t addr, blk;
@@ -1580,11 +1606,15 @@ swap_pager_putpages(vm_object_t object, vm_page_t *ma, int count,
continue;
}
VM_OBJECT_WLOCK(object);
+ swblk_iter_init_only(&blks, object);
for (j = 0; j < n; ++j) {
mreq = ma[i + j];
vm_page_aflag_clear(mreq, PGA_SWAP_FREE);
- addr = swp_pager_meta_build(mreq->object, mreq->pindex,
- blk + j, false);
+ KASSERT(mreq->object == object,
+ ("%s: object mismatch %p/%p",
+ __func__, mreq->object, object));
+ addr = swp_pager_meta_build(&blks, object,
+ mreq->pindex, blk + j, false);
if (addr != SWAPBLK_NONE)
swp_pager_update_freerange(&range, addr);
MPASS(mreq->dirty == VM_PAGE_BITS_ALL);
@@ -2102,19 +2132,18 @@ swp_pager_free_empty_swblk(vm_object_t object, struct swblk *sb)
* any.
*/
static daddr_t
-swp_pager_meta_build(vm_object_t object, vm_pindex_t pindex, daddr_t swapblk,
- bool nowait_noreplace)
+swp_pager_meta_build(struct pctrie_iter *blks, vm_object_t object,
+ vm_pindex_t pindex, daddr_t swapblk, bool nowait_noreplace)
{
static volatile int swblk_zone_exhausted, swpctrie_zone_exhausted;
struct swblk *sb, *sb1;
- vm_pindex_t modpi, rdpi;
+ vm_pindex_t modpi;
daddr_t prev_swapblk;
int error, i;
VM_OBJECT_ASSERT_WLOCKED(object);
- rdpi = rounddown(pindex, SWAP_META_PAGES);
- sb = swblk_lookup(object, rdpi);
+ sb = swblk_iter_lookup(blks, pindex);
if (sb == NULL) {
if (swapblk == SWAPBLK_NONE)
return (SWAPBLK_NONE);
@@ -2122,7 +2151,7 @@ swp_pager_meta_build(vm_object_t object, vm_pindex_t pindex, daddr_t swapblk,
sb = uma_zalloc(swblk_zone, M_NOWAIT | (curproc ==
pageproc ? M_USE_RESERVE : 0));
if (sb != NULL) {
- sb->p = rdpi;
+ sb->p = rounddown(pindex, SWAP_META_PAGES);
for (i = 0; i < SWAP_META_PAGES; i++)
sb->d[i] = SWAPBLK_NONE;
if (atomic_cmpset_int(&swblk_zone_exhausted,
@@ -2143,17 +2172,17 @@ swp_pager_meta_build(vm_object_t object, vm_pindex_t pindex, daddr_t swapblk,
} else
uma_zwait(swblk_zone);
VM_OBJECT_WLOCK(object);
- sb = swblk_lookup(object, rdpi);
+ sb = swblk_iter_reinit(blks, object, pindex);
if (sb != NULL)
/*
* Somebody swapped out a nearby page,
- * allocating swblk at the rdpi index,
+ * allocating swblk at the pindex index,
* while we dropped the object lock.
*/
goto allocated;
}
for (;;) {
- error = swblk_lookup_insert(object, sb);
+ error = swblk_iter_insert(blks, sb);
if (error == 0) {
if (atomic_cmpset_int(&swpctrie_zone_exhausted,
1, 0))
@@ -2175,7 +2204,7 @@ swp_pager_meta_build(vm_object_t object, vm_pindex_t pindex, daddr_t swapblk,
} else
uma_zwait(swpctrie_zone);
VM_OBJECT_WLOCK(object);
- sb1 = swblk_lookup(object, rdpi);
+ sb1 = swblk_iter_reinit(blks, object, pindex);
if (sb1 != NULL) {
uma_zfree(swblk_zone, sb);
sb = sb1;
@@ -2184,7 +2213,7 @@ swp_pager_meta_build(vm_object_t object, vm_pindex_t pindex, daddr_t swapblk,
}
}
allocated:
- MPASS(sb->p == rdpi);
+ MPASS(sb->p == rounddown(pindex, SWAP_META_PAGES));
modpi = pindex % SWAP_META_PAGES;
/* Return prior contents of metadata. */
@@ -2196,8 +2225,11 @@ allocated:
/*
* Free the swblk if we end up with the empty page run.
*/
- if (swapblk == SWAPBLK_NONE)
- swp_pager_free_empty_swblk(object, sb);
+ if (swapblk == SWAPBLK_NONE &&
+ swp_pager_swblk_empty(sb, 0, SWAP_META_PAGES)) {
+ swblk_iter_remove(blks);
+ uma_zfree(swblk_zone, sb);
+ }
}
return (prev_swapblk);
}
@@ -2213,7 +2245,7 @@ static void
swp_pager_meta_transfer(vm_object_t srcobject, vm_object_t dstobject,
vm_pindex_t pindex, vm_pindex_t count)
{
- struct pctrie_iter blks;
+ struct pctrie_iter dstblks, srcblks;
struct page_range range;
struct swblk *sb;
daddr_t blk, d[SWAP_META_PAGES];
@@ -2231,15 +2263,16 @@ swp_pager_meta_transfer(vm_object_t srcobject, vm_object_t dstobject,
swp_pager_init_freerange(&range);
d_mask = 0;
last = pindex + count;
- for (sb = swblk_iter_limit_init(&blks, srcobject, pindex, last),
+ swblk_iter_init_only(&dstblks, dstobject);
+ for (sb = swblk_iter_limit_init(&srcblks, srcobject, pindex, last),
start = swblk_start(sb, pindex);
- sb != NULL; sb = swblk_iter_next(&blks), start = 0) {
- limit = MIN(last - blks.index, SWAP_META_PAGES);
+ sb != NULL; sb = swblk_iter_next(&srcblks), start = 0) {
+ limit = MIN(last - srcblks.index, SWAP_META_PAGES);
for (i = start; i < limit; i++) {
if (sb->d[i] == SWAPBLK_NONE)
continue;
- blk = swp_pager_meta_build(dstobject,
- blks.index + i - pindex, sb->d[i], true);
+ blk = swp_pager_meta_build(&dstblks, dstobject,
+ srcblks.index + i - pindex, sb->d[i], true);
if (blk == sb->d[i]) {
/*
* Failed memory allocation stopped transfer;
@@ -2256,7 +2289,7 @@ swp_pager_meta_transfer(vm_object_t srcobject, vm_object_t dstobject,
}
if (swp_pager_swblk_empty(sb, 0, start) &&
swp_pager_swblk_empty(sb, limit, SWAP_META_PAGES)) {
- swblk_iter_remove(&blks);
+ swblk_iter_remove(&srcblks);
uma_zfree(swblk_zone, sb);
}
if (d_mask != 0) {
@@ -2264,8 +2297,8 @@ swp_pager_meta_transfer(vm_object_t srcobject, vm_object_t dstobject,
VM_OBJECT_WUNLOCK(srcobject);
do {
i = ffs(d_mask) - 1;
- swp_pager_meta_build(dstobject,
- blks.index + i - pindex, d[i], false);
+ swp_pager_meta_build(&dstblks, dstobject,
+ srcblks.index + i - pindex, d[i], false);
d_mask &= ~(1 << i);
} while (d_mask != 0);
VM_OBJECT_WLOCK(srcobject);
@@ -2274,7 +2307,7 @@ swp_pager_meta_transfer(vm_object_t srcobject, vm_object_t dstobject,
* While the lock was not held, the iterator path could
* have become stale, so discard it.
*/
- pctrie_iter_reset(&blks);
+ pctrie_iter_reset(&srcblks);
}
}
swp_pager_freeswapspace(&range);