Subject: bug#69241: [PATCH] Jsonrpc: improve performance of process filter function

From: Daniel Pettersson <[email-masked]>
Date: Sun, 18 Feb 2024 02:53:01 +0100

Tags: patch

This was issue was discovered during elpa package dape's development,
where an adapter was sending 72000 notifications on startup which leads
to emacs looping over timer--time-less-p for > 50 seconds and after the
fix for less then 1 second.  The "integrity" of timer order are messed
with but as timer_check runs all of the ripe timers in the same while
loop it only becomes an question of execution order.  This change uses
timer.el internal api `timer--triggered', but this might be fine as it's
tightly coupled with keyboard.

In GNU Emacs 30.0.50 (build 1, aarch64-apple-darwin23.1.0, NS
 appkit-2487.20 Version 14.1.1 (Build 23B81)) of 2023-12-20 built on
 Daniels-Air
Repository revision: 281be72422f42fcc84d43f50723a3e91b7d03cbc
Repository branch: master
Windowing system distributor 'Apple', version 10.3.2487
System Description:  macOS 14.1.1

>From 92eef1a5221dd69dc95a9484eafeacad571246f8 Mon Sep 17 00:00:00 2001
From: Daniel Pettersson <[email-masked]>
Date: Sun, 18 Feb 2024 02:05:46 +0100
Subject: [PATCH] Jsonrpc: improve performance of process filter function

`run-at-time' keeps `timer-list' list sorted by inserting each timer
based on the timer value.  This means that `timer--time-less-p' needs is
executed ~ N*N/2 times for each N pending messages.  This means that
jsonrpc becomes unusable for connections that generate a lot messages at
the same time.

* lisp/jsonrpc.el (Version): Bump to 1.0.25
(jsonrpc--process-filter): Improve performance
---
 lisp/jsonrpc.el | 21 ++++++++++++++++-----
 1 file changed, 16 insertions(+), 5 deletions(-)

diff --git a/lisp/jsonrpc.el b/lisp/jsonrpc.el
index 14fe0447008..9a52b5a76cf 100644
--- a/lisp/jsonrpc.el
+++ b/lisp/jsonrpc.el
@@ -4,7 +4,7 @@
 
 ;; Author: João Távora <[email-masked]>
 ;; Keywords: processes, languages, extensions
-;; Version: 1.0.24
+;; Version: 1.0.25
 ;; Package-Requires: ((emacs "25.2"))
 
 ;; This is a GNU ELPA :core package.  Avoid functionality that is not
@@ -782,11 +782,22 @@ jsonrpc--process-filter
           ;; non-locally (typically the reply to a request), so do
           ;; this all this processing in top-level loops timer.
           (cl-loop
+           with time = (timer-relative-time nil 0)
            for msg = (pop (process-get proc 'jsonrpc-mqueue)) while msg
-           do (run-at-time 0 nil
-                           (lambda (m) (with-temp-buffer
-                                         (jsonrpc-connection-receive conn m)))
-                           msg)))))))
+           do (let ((timer (timer-create)))
+                (timer-set-time timer time)
+                (timer-set-function timer
+                                    (lambda (conn msg)
+                                      (with-temp-buffer
+                                        (jsonrpc-connection-receive conn msg)))
+                                    (list conn msg))
+                (setf (timer--triggered timer) nil)
+                ;; We're bypassing `timer-activate' due to performance
+                ;; concerns.  `timer-activate' iterates through all
+                ;; timers scheduled to execute before inserting our
+                ;; callback.  While it doesn't maintain the precise
+                ;; order of timers, we should be fine.
+                (setf timer-list (cons timer timer-list)))))))))
 
 (defun jsonrpc--remove (conn id &optional deferred-spec)
   "Cancel CONN's continuations for ID, including its timer, if it exists.
-- 
2.39.3 (Apple Git-145)