> Yeah, I think we default to a 10% "dirty background memory" (and
> allows up to 20% dirty), so on your 16GB machine, we allow up to 1.6GB
> of dirty memory for writeout before we even start writing, and twice
> that before we start *waiting* for it.
>
> On 32-bit x86, we only count the memory in the low 1GB (really
> actually up to about 890MB), so "10% dirty" really means just about
> 90MB of buffering (and a "hard limit" of ~180MB of dirty).
>
=> On 32-bit system, the page cache also can use the high memory, so  the
size of 10% "dirty background memory" maybe 1.6GB for this case.

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