Re: how do file-mapped (mmapped) pages become dirty?

[Helge Hafting]

Amir Hermelin wrote:
> Hi,
> When a process mmaps a file, how does the kernel know the memory has been
> written to (and hence the page is dirty)? Is this done by setting the
> protected flag, and when the memory is first written to it's set to dirty?

No need on a i386.  The cpu sets the page dirty in the pagetables
when it is written to.  It doesn't matter what kind of page
it is.

> What function is responsible for this setting? And when will the page be
> written back to disk (i.e. where's the flusher located)?
When there's memory pressure, or a sync.

Helge Hafting

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