making my slow mac fast
Sunday, March 19, 2006 at 3:02PM My 867 Mhz, 512 mb ram 15" titanium powerbook g4 is not slow. The key to getting this four year old to perform is to understand and take advantage of OS X's virtual memory structure. (Oversimplifications follow, but they get the job done; my mac feels fast.)
Virtual memory is on disk; physical memory is on chips. Chips are faster than disk. To run, an application must be in physical memory. When switching applications, the new application must be "swapped in" to physical memory. If that physical memory was in use by another application, that application must be "swapped out." A standard mac-ish application takes about 100 mb of memory. Switching between a paged-in application and a paged-out application involves writing ~100 mb to disk, and reading another 100 mb from disk. 200 mb of disk access takes a non-trivial amount of time... enough to explain that annoying pause when I hit cmd-tab or click on another icon in the dock.
Running fewer applications requires less application switching, so it feels faster. This brings me to my key insight for the day: For improved performance on low-memory systems, use web apps in the browser to replace traditional desktop apps. Firefox is faster at switching between windows and tabs (all resident in physical memory, presumably) than OS X is at swapping applications between physical and virtual memory. Did someone say "the network is the computer"?
This approach is great for the things that I need to do with a portable machine: coding (editing text files on the server, using Transmit and BBEedit), email (although Mail.app can be rather slow on big mailboxes; I should probably switch to Laszlo Mail soon), and web browsing. Photoshop, no way; I don't even have photoshop installed on this machine. Nor do I run tomcat or an Open Laszlo server on this machine. I offload those jobs to the right machines, which I have access to because my employer understands: a blazing dual-opteron linux server for tomcat and OLS, and a bomber dual-2 G5 tower at work.
Diagnosing where my memory is going is possible using top, and easy using Activity Monitor or iPulse. I learned that Adium uses an astonishing amount of memory, as do dashboard clients. This mac is going to be my portable machine for a long time yet, so, goodbye Adium, goodbye cute dashboard widgets... Hello, terminal, my old friend!
Reader Comments (2)
It's so true. Chips are faster than iron.
Then again, is iron faster than broadband?
Thank you for this- it never occured to me that my dashboard widgets might be slowing my computer- out of sight, out of mind, right?
I closed them all and now my dear sweet Tinkerbelle is running a lot faster.