From c8209632eef6c31713f53d6af7a6b2eb8184c07a Mon Sep 17 00:00:00 2001
From: Joe Bryan <joemfb@gmail.com>
Date: Wed, 31 May 2023 16:33:59 -0400
Subject: [PATCH] u3: specify madv_random for file-backed snapshot mapping

---
 pkg/noun/events.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/pkg/noun/events.c b/pkg/noun/events.c
index 79f3ed1143..1cd1771d49 100644
--- a/pkg/noun/events.c
+++ b/pkg/noun/events.c
@@ -995,6 +995,11 @@ _ce_loom_mapf_north(c3_i fid_i, c3_w pgs_w, c3_w old_w)
                       pgs_w, strerror(errno));
       u3_assert(0);
     }
+
+    if ( -1 == madvise(_ce_ptr(0), _ce_len(pgs_w), MADV_RANDOM) ) {
+        fprintf(stderr, "loom: madv_random failed (%u pages): %s\r\n",
+                        pgs_w, strerror(errno));
+    }
   }
 
   if ( old_w > pgs_w ) {