From c82382ea2c213c59d5b1f5e006c3221f6fb61008 Mon Sep 17 00:00:00 2001
From: Jason Volk <jason@zemos.net>
Date: Thu, 27 Dec 2018 16:13:49 -0800
Subject: [PATCH] ircd::db: Use a zero soft-limit to yield all requests when
 saturated; prefetch condition.

---
 ircd/db.cc | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/ircd/db.cc b/ircd/db.cc
index dad930aa1..d7c58242e 100644
--- a/ircd/db.cc
+++ b/ircd/db.cc
@@ -109,6 +109,7 @@ ircd::db::request
 	"db req",
 	size_t(request_pool_stack_size),
 	0, // don't prespawn because this is static
+	0, // zero-size queue will yield submitter
 };
 
 /// This mutex is necessary to serialize entry into rocksdb's write impl
@@ -9859,6 +9860,9 @@ ircd::db::prefetch(column &column,
 	if(cached(column, key, gopts))
 		return;
 
+	if(!request.avail())
+		return;
+
 	request([column(column), key(std::string(key)), gopts]
 	() mutable
 	{