[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [xen master] xen/gnttab: reduce size of struct active_grant_entry
commit a2f520314169fdaa47ab19b2ca8fb9d9f1554a36 Author: Juergen Gross <jgross@xxxxxxxx> AuthorDate: Fri Dec 2 10:28:33 2022 +0100 Commit: Jan Beulich <jbeulich@xxxxxxxx> CommitDate: Fri Dec 2 10:28:33 2022 +0100 xen/gnttab: reduce size of struct active_grant_entry 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 <jgross@xxxxxxxx> Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx> --- 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 fa28c3cb7b..b896f9af0e 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; /* Original 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; } } @@ -2497,7 +2497,8 @@ 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; } @@ -2659,7 +2660,7 @@ 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)) ) { @@ -2692,7 +2693,7 @@ 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); @@ -2754,7 +2755,7 @@ 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; } -- generated by git-patchbot for /home/xen/git/xen.git#master
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