From 7a42187ccd7cf0f500b94aae2e4b3867d80d88e1 Mon Sep 17 00:00:00 2001
From: Chris Miller <chris.miller@quantumblack.com>
Date: Mon, 3 Dec 2018 19:03:27 -0500
Subject: [PATCH 1/2] Optimize Base64 encoding of large files to be uploaded to
 avoid GC pauses.

---
 notebook/static/tree/js/notebooklist.js | 19 +++++++++++++------
 1 file changed, 13 insertions(+), 6 deletions(-)

diff --git a/notebook/static/tree/js/notebooklist.js b/notebook/static/tree/js/notebooklist.js
index 8469caf73..18122aa68 100644
--- a/notebook/static/tree/js/notebooklist.js
+++ b/notebook/static/tree/js/notebooklist.js
@@ -1365,18 +1365,25 @@ define([
                             reader.onerror = on_error;
                         };
 
+                        // This approach avoids triggering multiple GC pauses for large files.
+                        // Borrowed from kanaka's answer at:
+                        // https://stackoverflow.com/questions/12710001/how-to-convert-uint8-array-to-base64-encoded-string
+                        var  Uint8ToString = function(u8a){
+                            var CHUNK_SZ = 0x8000;
+                            var c = [];
+                            for (var i=0; i < u8a.length; i+=CHUNK_SZ) {
+                              c.push(String.fromCharCode.apply(null, u8a.subarray(i, i+CHUNK_SZ)));
+                            }
+                            return c.join("");
+                        };
+
                         // These codes to upload file in original class
                         var upload_file = function(item, chunk) {
                             var filedata = item.data('filedata');
                             if (filedata instanceof ArrayBuffer) {
                                 // base64-encode binary file data
-                                var bytes = '';
                                 var buf = new Uint8Array(filedata);
-                                var nbytes = buf.byteLength;
-                                for (var i=0; i<nbytes; i++) {
-                                    bytes += String.fromCharCode(buf[i]);
-                                }
-                                filedata = btoa(bytes);
+                                filedata = btoa(Uint8ToString(buf));
                                 format = 'base64';
                             }
                             var model = { name: filename, path: path };

From daa80ad4ac7c27ccc8e8204283520184788b3ca3 Mon Sep 17 00:00:00 2001
From: Chris Miller <chris.miller@quantumblack.com>
Date: Mon, 3 Dec 2018 19:04:12 -0500
Subject: [PATCH 2/2] Tune chunk size for large file uploads to be larger for
 perf gains.

---
 notebook/static/tree/js/notebooklist.js | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/notebook/static/tree/js/notebooklist.js b/notebook/static/tree/js/notebooklist.js
index 18122aa68..7753a56dd 100644
--- a/notebook/static/tree/js/notebooklist.js
+++ b/notebook/static/tree/js/notebooklist.js
@@ -1314,7 +1314,8 @@ define([
 
                     var parse_large_file = function (f, item) {
                         // codes inspired by https://stackoverflow.com/a/28318964
-                        var chunk_size = 1024 * 1024;
+                        // 8MB chunk size chosen to match chunk sizes used by benchmark reference (AWS S3)
+                        var chunk_size = 1024 * 1024 * 8;
                         var offset = 0;
                         var chunk = 0;
                         var chunk_reader = null;