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iommu_gas: Change find_space lower search order

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iommu_gas_lowermatch looks right, then left, then right again in its
search for free space.  Change to a more straightforward last-fit
search that touches fewer tree nodes and improves performance.

Reported by:	wxzhu@rice.edu
Reviewed by:	alc, kib
MFC after:	3 weeks
Differential Revision:	https://reviews.freebsd.org/D35439
This commit is contained in:
Doug Moore 2022-06-08 23:14:28 -05:00
parent 1d2e46d408
commit 3003117253
1 changed files with 8 additions and 10 deletions
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18
sys/dev/iommu/iommu_gas.c
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@ -377,14 +377,6 @@ iommu_gas_lowermatch(struct iommu_gas_match_args *a, struct iommu_map_entry *ent
{
struct iommu_map_entry *child;
child = RB_RIGHT(entry, rb_entry);
if (child != NULL && entry->end < a->common->lowaddr &&
iommu_gas_match_one(a, entry->end, child->first,
a->common->lowaddr)) {
iommu_gas_match_insert(a);
return (0);
}
/*
* If the subtree doesn't have free space for the requested allocation
* plus two guard pages, give up.
@ -393,16 +385,22 @@ iommu_gas_lowermatch(struct iommu_gas_match_args *a, struct iommu_map_entry *ent
return (ENOMEM);
if (entry->first >= a->common->lowaddr)
return (ENOMEM);
child = RB_LEFT(entry, rb_entry);
child = RB_RIGHT(entry, rb_entry);
if (child != NULL && 0 == iommu_gas_lowermatch(a, child))
return (0);
if (child != NULL && entry->end < a->common->lowaddr &&
iommu_gas_match_one(a, entry->end, child->first,
a->common->lowaddr)) {
iommu_gas_match_insert(a);
return (0);
}
child = RB_LEFT(entry, rb_entry);
if (child != NULL && child->last < a->common->lowaddr &&
iommu_gas_match_one(a, child->last, entry->start,
a->common->lowaddr)) {
iommu_gas_match_insert(a);
return (0);
}
child = RB_RIGHT(entry, rb_entry);
if (child != NULL && 0 == iommu_gas_lowermatch(a, child))
return (0);
return (ENOMEM);