X-Git-Url: https://git.arvados.org/arvados.git/blobdiff_plain/0e83a8971942943e79dfc1b064b5bac0cc82217f..bb39fb01d3147c6009ee35920ae0637201b11dd2:/services/fuse/arvados_fuse/fusedir.py

diff --git a/services/fuse/arvados_fuse/fusedir.py b/services/fuse/arvados_fuse/fusedir.py
index 4b20341638..f3816c0d3e 100644
--- a/services/fuse/arvados_fuse/fusedir.py
+++ b/services/fuse/arvados_fuse/fusedir.py
@@ -525,7 +525,12 @@ class CollectionDirectory(CollectionDirectoryBase):
                         self.collection.update()
                         new_collection_record = self.collection.api_response()
                     else:
-                        get_threads = max((self.api.keep.block_cache.cache_max // (64 * 1024 * 1024)) - 1, 0)
+                        # If there's too many prefetch threads and you
+                        # max out the CPU, delivering data to the FUSE
+                        # layer actually ends up being slower.
+                        # Experimentally, capping 7 threads seems to
+                        # be a sweet spot.
+                        get_threads = min(max((self.api.keep.block_cache.cache_max // (64 * 1024 * 1024)) - 1, 1), 7)
                         # Create a new collection object
                         if uuid_pattern.match(self.collection_locator):
                             coll_reader = arvados.collection.Collection(