Diagnosing a Latency Problem

Recently I started experiencing latency in emacs. I could tell the typing and the cursor movement felt slower. Interestingly, the problem seemed to worsen over time. At first I thought it was my mode line but enabling and re-enabling it had no effect. Then I considered whether it was some mode I had enabled. But I did not have any strange modes. I did not even have the usual suspect, text completion, enabled–other than abbrev-mode that is. Suddenly, it hit me: the log buffer. A while back I started logging all sorts of events in my Emacs configuration with lgr. The plan had been to enable logging all the time at first just to make sure it worked; and afterwards only while oo-debug-p was active. Later, however, I changed my mind. I thought it was not really costing me anything to leave the log on. On the contrary, it allowed me to quickly identify bugs. Therefore, I decided to just leave it on all the time. The way the logging worked was very simple: any message logged would simply write to a buffer named *log*. It is only now when considering my current performance issue that I realize that the log buffer unlike the *Message* buffer has no cap. The more logging, the larger and larger the buffer grows. And, I suspect, that at some point it would get so large that it would slow everything down. For now, I am disabling logging when oo-debug-p is false.

(defmacro info! (msg &rest meta)
  (when oo-debug-p
    `(lgr-info oo-logger ,msg ,@meta)))

(defmacro error! (msg &rest meta)
  (when oo-debug-p
    `(lgr-error oo-error-logger ,msg ,@meta)))

(defmacro warn! (msg &rest meta)
  (when oo-debug-p
    `(lgr-warn oo-logger ,msg ,@meta)))

(defmacro fatal! (msg &rest meta)
  (when oo-debug-p
    `(lgr-fatal oo-logger ,msg ,@meta)))

(defmacro trace! (msg &rest meta)
  (when oo-debug-p
    `(lgr-trace oo-logger ,msg ,@meta)))

(defmacro debug! (msg &rest meta)
  (when oo-debug-p
    `(lgr-debug oo-logger ,msg ,@meta)))

This is more of a band-aid until I can think of something better than a full-blown solution. Logging has proved so useful I would like to see it all the time.