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swap_pager: small improvement to find_least

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Drop an unneeded test, a branch and a needless computation to save a
few instructions.

Reviewed by:	kib
Differential Revision:	https://reviews.freebsd.org/D45558
This commit is contained in:
Doug Moore 2024-06-11 11:36:23 -05:00
parent 0277c0c6f7
commit dd0e5c02ab
1 changed files with 7 additions and 12 deletions
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19
sys/vm/swap_pager.c
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@ -2289,22 +2289,17 @@ swap_pager_find_least(vm_object_t object, vm_pindex_t pindex)
VM_OBJECT_ASSERT_LOCKED(object);
MPASS((object->flags & OBJ_SWAP) != 0);
if (pctrie_is_empty(&object->un_pager.swp.swp_blks))
return (object->size);
sb = SWAP_PCTRIE_LOOKUP_GE(&object->un_pager.swp.swp_blks,
rounddown(pindex, SWAP_META_PAGES));
if (sb == NULL)
return (object->size);
if (sb->p < pindex) {
for (i = pindex % SWAP_META_PAGES; i < SWAP_META_PAGES; i++) {
if (sb->d[i] != SWAPBLK_NONE)
return (sb->p + i);
}
sb = SWAP_PCTRIE_LOOKUP_GE(&object->un_pager.swp.swp_blks,
roundup(pindex, SWAP_META_PAGES));
if (sb == NULL)
return (object->size);
for (i = pindex - sb->p; i < SWAP_META_PAGES; i++) {
if (sb->d[i] != SWAPBLK_NONE)
return (sb->p + i);
}
sb = SWAP_PCTRIE_LOOKUP_GE(&object->un_pager.swp.swp_blks, pindex);
if (sb == NULL)
return (object->size);
for (i = 0; i < SWAP_META_PAGES; i++) {
if (sb->d[i] != SWAPBLK_NONE)
return (sb->p + i);
@ -2314,7 +2309,7 @@ swap_pager_find_least(vm_object_t object, vm_pindex_t pindex)
* We get here if a swblk is present in the trie but it
* doesn't map any blocks.
*/
MPASS(0);
__unreachable();
return (object->size);
}