Why doesn't the kernel writeback all the time?
Posted Jun 6, 2013 6:10 UTC (Thu) by gmatht
Parent article: Atomic I/O operations
"Since the system in question had a fair amount of memory, the normal asynchronous writeback mechanism didn't kick in, so dirty blocks were not being written steadily"
I've noticed that behavior too. It seems strange that adding more memory for write buffers would reduce performance. One can of course tell the kernel to limit the size of the write buffers, but why would the kernel leave the disk essentially idle while buffers are filling up? Wouldn't it give better performance to utilize periods of idle-ish I/O to write dirty buffers? Or is this strategy intended to reduce power consumption?
I suspect I am missing something.
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