A Different Kind of Optimization2018-07-04
Attempting to analyze and profile one of my projects I've come to appreciate an orthogonal solution to the need for speed.
How Much Speed Do You Need?
I've written previously about profiling my own static site generator, at which point I measured generating this entire weblog to take 5⁄10ths of a second, and then identified a fix to reduce things by about 25%.
Currently that measure is a bit slower, as a result of more content to regenerate. With about 56 posts spanning several years the entire site now takes:
$ time -v quiescent Command being timed: "quiescent" User time (seconds): 0.33 System time (seconds): 0.05 Percent of CPU this job got: 61% Elapsed (wall clock) time (h:mm:ss or m:ss): 0:00.64 Average shared text size (kbytes): 0 Average unshared data size (kbytes): 0 Average stack size (kbytes): 0 Average total size (kbytes): 0 Maximum resident set size (kbytes): 93552640 Average resident set size (kbytes): 0 Major (requiring I/O) page faults: 0 Minor (reclaiming a frame) page faults: 6450 Voluntary context switches: 0 Involuntary context switches: 543 Swaps: 0 File system inputs: 0 File system outputs: 0 Socket messages sent: 0 Socket messages received: 0 Signals delivered: 0 Page size (bytes): 4096 Exit status: 0
About 6⁄10ths of second.
Without thinking too deeply about the problem, I considered using
module, specifically with either a
threadPoolExecutor. The idea being, multiple processes or threads
could operate on "posts" independently and reduce time spent in IO of
reading and writing files.
After prototyping out a test with both I didn't see appreciable gains
because a significant portion of time is in file IO across multiple
function calls, so there is no easy-win to be had by simply invoking
executor.map (which shouldn't really be surprising). Combined with
the fact that there is an overhead to both, I dismissed both
prototypes as over-architecting a solution. I still think there is a
potential solution here, possibly creating a thread pool in the
Static class and using it for all IO (reading raw data and writing
formatted posts), rather than just reading posts, which is what I
A Novel Approach
In absolute terms, 6⁄10ths of a second is
not very long. The issue is that immediate feedback feels slow as a
result of the visual "hang" that occurs after your type
and then hit ENTER. This is more a user-experience issue than an
engineering problem. With that in mind I installed
fswatch which is like a
cross-platform version of
inotify. I thought that if I wasn't
manually invoking the command to rebuild, I probably wouldn't care
much how long it takes. It doesn't solve the problem of generation
times, but what it does is make it invisible.
I setup a "watch" on the
posts directory, which accomplishes a
notification on file-save events, from there an infinite loop on
read (which blocks on input) rebuilds the site via the
$ fswatch posts/ | while read _; do quiescent done
A Good Enough Solution
Applescript is, to be honest, pretty terrible, but I may have finally
found a legitimate-to-me use for it though (I save the following to a
tell application "Google Chrome" to tell the active tab of its first window reload end tell
What this does is refresh the current browser tab in Google Chrome without losing page position or requiring the application take window focus. My only regret is that I haven't found a similar solution for Firefox.
From the top-level of the weblog tree, I'll start a local web-server in the build directory and background it:
$ cd build; python -m http-server &; cd -
Modifying the re-build pipeline from above with the Applescript achieves a rebuild pipeline that requires no interaction on my part:
$ fswatch posts/ | while read _; do quiescent; osascript refresh-tab.script; done
What that looks like in practice:
I think a big part of why this appeals to me is that it avoids over-complicating my static site generator. I didn't incorporate automatic refreshes, a local web-server, or file-watching into my project, I built up a custom solution using small, focused tools.