Daniel P. Berrangé <berra...@redhat.com> pointed out that the coroutine
pool size heuristic is very conservative. Instead of halving
max_map_count, he suggested reserving 5,000 mappings for non-coroutine
users based on observations of guests he has access to.
Fixes: 86a637e48104 ("coroutine: cap per-thread local pool size")
Signed-off-by: Stefan Hajnoczi <stefa...@redhat.com>
Reviewed-by: Daniel P. Berrangé <berra...@redhat.com>
Message-id: 20240320181232.1464819-1-stefa...@redhat.com
Signed-off-by: Stefan Hajnoczi <stefa...@redhat.com>
---
util/qemu-coroutine.c | 15 ++++++++++-----
1 file changed, 10 insertions(+), 5 deletions(-)
diff --git a/util/qemu-coroutine.c b/util/qemu-coroutine.c
index 2790959eaf..eb4eebefdf 100644
--- a/util/qemu-coroutine.c
+++ b/util/qemu-coroutine.c
@@ -377,12 +377,17 @@ static unsigned int get_global_pool_hard_max_size(void)
NULL) &&
qemu_strtoi(contents, NULL, 10, &max_map_count) == 0) {
/*
- * This is a conservative upper bound that avoids exceeding
- * max_map_count. Leave half for non-coroutine users like library
- * dependencies, vhost-user, etc. Each coroutine takes up 2 VMAs so
- * halve the amount again.
+ * This is an upper bound that avoids exceeding max_map_count. Leave a
+ * fixed amount for non-coroutine users like library dependencies,
+ * vhost-user, etc. Each coroutine takes up 2 VMAs so halve the
+ * remaining amount.
*/
- return max_map_count / 4;
+ if (max_map_count > 5000) {
+ return (max_map_count - 5000) / 2;
+ } else {
+ /* Disable the global pool but threads still have local pools */
+ return 0;
+ }
}
#endif
--
2.44.0
