diff --git a/geojson.c b/geojson.c
index eee8268..6239394 100644
--- a/geojson.c
+++ b/geojson.c
@@ -916,6 +916,7 @@ void *run_sort(void *v) {
 
 		memcpy(map2, map, end - start);
 
+		// No madvise, since caller will want the sorted data
 		munmap(map, end - start);
 		munmap(map2, end - start);
 	}
@@ -1036,6 +1037,7 @@ void *run_read_parallel(void *v) {
 
 	do_read_parallel(map, a->len, a->offset, a->reading, a->reader, a->progress_seq, a->exclude, a->include, a->exclude_all, a->fname, a->basezoom, a->source, a->nlayers, a->droprate, a->initialized, a->initial_x, a->initial_y);
 
+	madvise(map, a->len, MADV_FREE);
 	if (munmap(map, a->len) != 0) {
 		perror("munmap source file");
 	}
@@ -1190,10 +1192,12 @@ void radix1(int *geomfds_in, int *indexfds_in, int inputs, int prefix, int split
 			fwrite_check(&ix, sizeof(struct index), 1, indexfiles[which], "index");
 		}
 
+		madvise(indexmap, indexst.st_size, MADV_FREE);
 		if (munmap(indexmap, indexst.st_size) < 0) {
 			perror("unmap index");
 			exit(EXIT_FAILURE);
 		}
+		madvise(geommap, geomst.st_size, MADV_FREE);
 		if (munmap(geommap, geomst.st_size) < 0) {
 			perror("unmap geom");
 			exit(EXIT_FAILURE);
@@ -1295,10 +1299,12 @@ void radix1(int *geomfds_in, int *indexfds_in, int inputs, int prefix, int split
 
 				merge(merges, nmerges, (unsigned char *) indexmap, indexfile, bytes, indexpos / bytes, geommap, geomfile, geompos_out, progress, progress_max, progress_reported);
 
+				madvise(indexmap, indexst.st_size, MADV_FREE);
 				if (munmap(indexmap, indexst.st_size) < 0) {
 					perror("unmap index");
 					exit(EXIT_FAILURE);
 				}
+				madvise(geommap, geomst.st_size, MADV_FREE);
 				if (munmap(geommap, geomst.st_size) < 0) {
 					perror("unmap geom");
 					exit(EXIT_FAILURE);
@@ -1333,10 +1339,12 @@ void radix1(int *geomfds_in, int *indexfds_in, int inputs, int prefix, int split
 					fwrite_check(&ix, sizeof(struct index), 1, indexfile, "index");
 				}
 
+				madvise(indexmap, indexst.st_size, MADV_FREE);
 				if (munmap(indexmap, indexst.st_size) < 0) {
 					perror("unmap index");
 					exit(EXIT_FAILURE);
 				}
+				madvise(geommap, geomst.st_size, MADV_FREE);
 				if (munmap(geommap, geomst.st_size) < 0) {
 					perror("unmap geom");
 					exit(EXIT_FAILURE);
@@ -1606,6 +1614,7 @@ int read_json(int argc, struct source **sourcelist, char *fname, const char *lay
 			overall_offset += st.st_size - off;
 
 			if (munmap(map, st.st_size - off) != 0) {
+				madvise(map, st.st_size, MADV_FREE);
 				perror("munmap source file");
 			}
 		} else {
@@ -1852,6 +1861,7 @@ int read_json(int argc, struct source **sourcelist, char *fname, const char *lay
 				perror("Reunify meta");
 				exit(EXIT_FAILURE);
 			}
+			madvise(map, reader[i].metapos, MADV_FREE);
 			if (munmap(map, reader[i].metapos) != 0) {
 				perror("unmap unmerged meta");
 			}
@@ -2122,6 +2132,7 @@ int read_json(int argc, struct source **sourcelist, char *fname, const char *lay
 			}
 		}
 
+		madvise(map, indexpos, MADV_FREE);
 		munmap(map, indexpos);
 	}
 
@@ -2163,6 +2174,7 @@ int read_json(int argc, struct source **sourcelist, char *fname, const char *lay
 		ret = EXIT_FAILURE;
 	}
 
+	madvise(meta, metapos, MADV_FREE);
 	if (munmap(meta, metapos) != 0) {
 		perror("munmap meta");
 	}
@@ -2171,6 +2183,7 @@ int read_json(int argc, struct source **sourcelist, char *fname, const char *lay
 	}
 
 	if (poolpos > 0) {
+		madvise(pool, poolpos, MADV_FREE);
 		if (munmap(stringpool, poolpos) != 0) {
 			perror("munmap stringpool");
 		}
diff --git a/tile.cc b/tile.cc
index 3fe1e8a..f3cbeb0 100644
--- a/tile.cc
+++ b/tile.cc
@@ -1152,6 +1152,7 @@ void *run_thread(void *vargs) {
 			}
 		}
 
+		madvise(geomstart, arg->geom_size[j], MADV_FREE);
 		if (munmap(geomstart, arg->geom_size[j]) != 0) {
 			perror("munmap geom");
 		}