The size of struct active_grant_entry for 64-bit builds is 40 or 48
bytes today (with or without NDEBUG).
It can easily be reduced by 8 bytes by replacing the trans_domain
pointer with the domid of the related domain. trans_domain is only ever
used for transitive grants, which doesn't have any known users.
This reduction will result in less memory usage and (for production
builds) in faster code, as indexing into the active_grant_entry array
will be much easier with an entry having a power-of-2 size.
The performance loss when using transitive grants shouldn't really
matter, given the probability that those aren't in use at all.
Signed-off-by: Juergen Gross <jgr...@suse.com>
---
V2:
- rename trans_domid to src_domid (Jan Beulich)
---
xen/common/grant_table.c | 13 +++++++------
1 file changed, 7 insertions(+), 6 deletions(-)
diff --git a/xen/common/grant_table.c b/xen/common/grant_table.c
index fba329dcc2..59342df3b7 100644
--- a/xen/common/grant_table.c
+++ b/xen/common/grant_table.c
@@ -381,13 +381,13 @@ struct active_grant_entry {
})
domid_t domid; /* Domain being granted access. */
+ domid_t src_domid; /* Domain granting access. */
unsigned int start:15; /* For sub-page grants, the start offset
in the page. */
bool is_sub_page:1; /* True if this is a sub-page grant. */
unsigned int length:16; /* For sub-page grants, the length of the
grant. */
grant_ref_t trans_gref;
- struct domain *trans_domain;
mfn_t mfn; /* Machine frame being granted. */
#ifndef NDEBUG
gfn_t gfn; /* Guest's idea of the frame being granted. */
@@ -1095,7 +1095,7 @@ map_grant_ref(
act->start = 0;
act->length = PAGE_SIZE;
act->is_sub_page = false;
- act->trans_domain = rd;
+ act->src_domid = rd->domain_id;
act->trans_gref = ref;
}
}
@@ -2494,7 +2494,8 @@ release_grant_for_copy(
else
{
status = &status_entry(rgt, gref);
- td = act->trans_domain;
+ td = (act->src_domid == rd->domain_id)
+ ? rd : knownalive_domain_from_domid(act->src_domid);
trans_gref = act->trans_gref;
}
@@ -2657,7 +2658,7 @@ acquire_grant_for_copy(
!mfn_eq(act->mfn, grant_mfn) ||
act->start != trans_page_off ||
act->length != trans_length ||
- act->trans_domain != td ||
+ act->src_domid != td->domain_id ||
act->trans_gref != trans_gref ||
!act->is_sub_page)) )
{
@@ -2676,7 +2677,7 @@ acquire_grant_for_copy(
act->domid = ldom;
act->start = trans_page_off;
act->length = trans_length;
- act->trans_domain = td;
+ act->src_domid = td->domain_id;
act->trans_gref = trans_gref;
act->mfn = grant_mfn;
act_set_gfn(act, INVALID_GFN);
@@ -2738,7 +2739,7 @@ acquire_grant_for_copy(
act->is_sub_page = is_sub_page;
act->start = trans_page_off;
act->length = trans_length;
- act->trans_domain = td;
+ act->src_domid = td->domain_id;
act->trans_gref = trans_gref;
act->mfn = grant_mfn;
}
--
2.35.3
