While doing some persistent testing against our product (the target is a system extension), we noticed huge memory usage (1Gig+) reported by the Activity Monitor. However when we sat down to actually profile the memory usage, we noticed Intruments tool only reported ~200MB overall usage against the same process (same PID). These 2 numbers were observed at the same time.
We knew that our system extension had processed some intense events during the persistent testing and its heap usage peaked at around 800 or perhaps 900MB at a time in the memory profiling; But since at the end of profiling the heap usage dropped to ~200MB I'd say we are good (we trust the Instruments result mostly). However how do we explain the fact Activity Monitor still reported the 1Gig usage (and I knew there were also confusion around the "real memory" or "private memory" stuff, the "1Gig" number referred here was from the "Memory" column from Activity Monitor)?
Mostly, our concern is that since the Activity Monitor is an end user facing utility, they'd potentially look at the big number and come back complaining about our memory usage. If this happens is it ok for us to explain that the actual memory usage by our program is less than what Activity Monitor shows?