Commit a06afe83 authored by Christian Borntraeger's avatar Christian Borntraeger Committed by Heiko Carstens

KVM: s390: vsie/gmap: reduce gmap_rmap overhead

there are cases that trigger a 2nd shadow event for the same
vmaddr/raddr combination. (prefix changes, reboots, some known races)
This will increase memory usages and it will result in long latencies
when cleaning up, e.g. on shutdown. To avoid cases with a list that has
hundreds of identical raddrs we check existing entries at insert time.
As this measurably reduces the list length this will be faster than
traversing the list at shutdown time.

In the long run several places will be optimized to create less entries
and a shrinker might be necessary.

Fixes: 4be130a0 ("s390/mm: add shadow gmap support")
Signed-off-by: default avatarChristian Borntraeger <borntraeger@linux.ibm.com>
Acked-by: default avatarDavid Hildenbrand <david@redhat.com>
Link: https://lore.kernel.org/r/20220429151526.1560-1-borntraeger@linux.ibm.comSigned-off-by: default avatarHeiko Carstens <hca@linux.ibm.com>
parent b5d12744
...@@ -1183,6 +1183,7 @@ EXPORT_SYMBOL_GPL(gmap_read_table); ...@@ -1183,6 +1183,7 @@ EXPORT_SYMBOL_GPL(gmap_read_table);
static inline void gmap_insert_rmap(struct gmap *sg, unsigned long vmaddr, static inline void gmap_insert_rmap(struct gmap *sg, unsigned long vmaddr,
struct gmap_rmap *rmap) struct gmap_rmap *rmap)
{ {
struct gmap_rmap *temp;
void __rcu **slot; void __rcu **slot;
BUG_ON(!gmap_is_shadow(sg)); BUG_ON(!gmap_is_shadow(sg));
...@@ -1190,6 +1191,12 @@ static inline void gmap_insert_rmap(struct gmap *sg, unsigned long vmaddr, ...@@ -1190,6 +1191,12 @@ static inline void gmap_insert_rmap(struct gmap *sg, unsigned long vmaddr,
if (slot) { if (slot) {
rmap->next = radix_tree_deref_slot_protected(slot, rmap->next = radix_tree_deref_slot_protected(slot,
&sg->guest_table_lock); &sg->guest_table_lock);
for (temp = rmap->next; temp; temp = temp->next) {
if (temp->raddr == rmap->raddr) {
kfree(rmap);
return;
}
}
radix_tree_replace_slot(&sg->host_to_rmap, slot, rmap); radix_tree_replace_slot(&sg->host_to_rmap, slot, rmap);
} else { } else {
rmap->next = NULL; rmap->next = NULL;
......
Markdown is supported
0%
or
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment