Mavericks

Design

Introduced skeuomorphism

Skeuomorphism is a design approach where digital interface elements mimic the look and feel of their real-world counterparts (e.g., a notepad app resembling lined paper) to make them more intuitive.

Power management

App nap

App Nap is a power-saving feature that automatically throttles and suspends backgrounded or off-screen applications when they aren’t actively in x, reducing CPU, disk, and network activity to extend battery life.

Timer coalescing

Timer coalescing is a macOS power‐management feature that batches and aligns disparate low‐priority timer events across processes to fire together, reducing CPU wakeups and improving energy efficiency.

[!NOTE] what are disparate low‐priority timer events? Disparate low‐priority timer events are independent, non-critical callbacks scheduled by different applications or system services—such as background maintenance tasks, periodic polling, or deferred updates—that don’t require precise timing.

CPU wake-ups are bad because they force the processor out of low-power sleep states, causing increased energy consumption, heat generation, and reduced battery life.

Compressed memory

Compressed memory is a macOS memory‐management feature that transparently compresses inactive RAM pages in place to reduce swap usage and improve performance.

[!NOTE] Alternative to compressed memory? The alternative to in-RAM compression is simply paging (swapping) inactive memory pages out to disk via macOS’s dynamic pager, though this is slower than keeping data compressed in RAM.

Why reduce swap usage?

Reducing swap usage avoids slow disk I/O operations—improving responsiveness, reducing latency and energy use, and prolonging storage device lifespan.

What is paging?

Paging is the memory‐management process of moving fixed‐size blocks of data (pages) between physical RAM and secondary storage (swap) to implement virtual memory.

macOS dynamic pager

macOS’s pager is dynamic because it automatically creates, expands, and removes swap files on demand and adjusts paging behavior in real time based on current memory pressure and system load.

  • Why didn’t compressed memory make sense on desktops?
    • Because traditional desktops had plenty of cheap RAM and fast swap storage, the CPU overhead of compressing and decompressing in-place didn’t justify the marginal memory savings.
  • how did it not benefit traditional desktops but benefit macOS?
    • Because traditional desktops typically had ample RAM and relied on fast disk-based swapping—making the CPU overhead of in-place compression unjustified—whereas macOS (especially on laptops with limited memory and SSD storage) gains significant performance, reduced I/O, and better battery life by compressing inactive pages in RAM.
  • Is this also why it benefited iOS?
    • Yes. It benefited iOS even more because mobile devices have far more constrained RAM and flash storage (with limited write endurance), so compressing inactive pages in RAM reduces costly swap I/O, improves performance, and extends battery life.

Threading

Thread-level Quality of Service (QoS)

TBD