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Sfink/Performance Thoughts: Difference between revisions
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More importantly, tools have a distinction of "I/O wait time" vs "CPU time". This distinction is mostly real: with I/O wait, your process is scheduled out and not running. CPU time includes time when the CPU is twiddling its thumbs waiting for a cache miss to be resolved, but the CPU isn't going anywhere; it'll keep running your process immediately after the needed data gets loaded in. (Even in SMT eg hyperthreading, where it is pulling from multiple threads all the time. When your process blocks on a cache miss, the scheduler will just pull instructions from the other thread for a while until you can start feeding it again.) | More importantly, tools have a distinction of "I/O wait time" vs "CPU time". This distinction is mostly real: with I/O wait, your process is scheduled out and not running. CPU time includes time when the CPU is twiddling its thumbs waiting for a cache miss to be resolved, but the CPU isn't going anywhere; it'll keep running your process immediately after the needed data gets loaded in. (Even in SMT eg hyperthreading, where it is pulling from multiple threads all the time. When your process blocks on a cache miss, the scheduler will just pull instructions from the other thread for a while until you can start feeding it again.) | ||
=== Locks === | |||
A process can also wait on locks. | |||
== Tasks == | == Tasks == | ||