We've covered a number of Gems for keeping an eye on your Mac's performance and activity, including MenuMeters, iPulse, and MemoryStick. I recently came across another useful option, MiniUsage, which makes some activity information easily accessible via a bit of space on your menu-bar.
With MiniUsage running, a small menu-bar display shows your choice of system-performance data: CPU usage (the percentage of your Mac's processing power that's currently in use), incoming network data rate, outgoing network data rate, or (on a laptop) battery. Alternatively, MiniUsage's display can rotate through these statistics, changing every few seconds. You choose how often the statistics are updated, from every second to every five seconds.
Click on the MiniUsage menu, and the program shows you a live-updated, sorted list of the processes using the most CPU resources, along with the percentage of CPU use for each; you choose how many processes are displayed, from one to 20. This is a great way to quickly see which programs and processes are bogging down your Mac's processor(s). Snow Leopard users can even switch to a program by choosing its name from the MiniUsage menu.
(One bug here is that if a process's name includes a space, the second word of the name appears in the CPU-percentage field instead of that percentage. The process appears in the correct location in the list, but you don't see the actual CPU-usage number.)
If your Mac has multiple processors or cores, the menu also displays what percentage of each core is currently being used; mouse over a core and a hierarchical menu shows how that usage is divided between system- and user-level processes.
The menu also displays the same network-throughput data you can opt to view in the menu bar, and mousing over the Detailed Information item in the menu shows you a pop-up view of the output of the top -l1 shell command (as if you'd entered that command in Terminal). Unfortunately, this display uses a proportional font, rather than a monospace one, so it's nearly impossible to read--especially in Snow Leopard, where the output of top -l1 is already nearly useless.
Two bits of info I'd like to see in MiniUsage are memory usage (total and by process, just as the program displays CPU usage) and the available space on each connected volume. But given that MiniUsage was released less than a month ago, it's a good bet the developer is already working on improving the program.
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This story, "MiniUsage Lets You Monitor Your Mac's Activity" was originally published by Macworld.