stream: do not unconditionally call `_read()` on `resume()`

`readable.resume()` calls `.read(0)`, which in turn previously set
`needReadable = true`, and so a subsequent `.read()` call would
call `_read()` even though enough data was already available.

This can lead to elevated memory usage, because calling `_read()`
when enough data is in the readable buffer means that backpressure
is not being honoured.

Fixes: https://github.com/nodejs/node/issues/26957

PR-URL: https://github.com/nodejs/node/pull/26965
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>

1 files changed, 1 insertions, 1 deletions

diff --git a/lib/_stream_readable.js b/lib/_stream_readable.js
index 3e46a604e5..cbbfd0ba59 100644
--- a/lib/_stream_readable.js
+++ b/lib/_stream_readable.js
@@ -475,7 +475,7 @@ Readable.prototype.read = function(n) {
     ret = null;
 
   if (ret === null) {
-    state.needReadable = true;
+    state.needReadable = state.length <= state.highWaterMark;
     n = 0;
   } else {
     state.length -= n;