d/freebsd-dev
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

iommu_gas: restrict tree search to promising paths

Browse Source 
In iommu_gas_lowermatch and iommu_gas_uppermatch, a subtree search is
quickly terminated if the largest available free space in the subtree
is below a limit, where that limit is related to the size of the
allocation request. However, that limit is too small; it does not
account for both of the guard pages that will surround the allocated
space, but only for one of them. Consequently, it permits the search
to proceed through nodes that cannot produce a successful allocation
for all the requested space. Fix that limit to improve search
performance.

Reviewed by:	alc, kib
Submitted by:	Weixi Zhu (wxzhu@rice.edu)
MFC after:	3 weeks
Differential Revision:	https://reviews.freebsd.org/D35414
This commit is contained in:
Doug Moore 2022-06-06 16:26:01 -05:00
parent 156745b42d
commit b831865fe3
1 changed files with 11 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

13
sys/dev/iommu/iommu_gas.c
View File

@ -384,7 +384,12 @@ iommu_gas_lowermatch(struct iommu_gas_match_args *a, struct iommu_map_entry *ent
iommu_gas_match_insert(a);
return (0);
}
if (entry->free_down < a->size + a->offset + IOMMU_PAGE_SIZE)
/*
* If the subtree doesn't have free space for the requested allocation
* plus two guard pages, give up.
*/
if (entry->free_down < a->size + a->offset + 2 * IOMMU_PAGE_SIZE)
return (ENOMEM);
if (entry->first >= a->common->lowaddr)
return (ENOMEM);
@ -408,7 +413,11 @@ iommu_gas_uppermatch(struct iommu_gas_match_args *a, struct iommu_map_entry *ent
{
struct iommu_map_entry *child;
if (entry->free_down < a->size + a->offset + IOMMU_PAGE_SIZE)
/*
* If the subtree doesn't have free space for the requested allocation
* plus two guard pages, give up.
*/
if (entry->free_down < a->size + a->offset + 2 * IOMMU_PAGE_SIZE)
return (ENOMEM);
if (entry->last < a->common->highaddr)
return (ENOMEM);