On 07/02/12 15:00, Nico Williams wrote:
On Mon, Jul 2, 2012 at 3:32 PM, Bob Friesenhahn
<>  wrote:
On Mon, 2 Jul 2012, Iwan Aucamp wrote:
I'm interested in some more detail on how ZFS intent log behaves for
updated done via a memory mapped file - i.e. will the ZIL log updates done
to an mmap'd file or not ?

I would to expect these writes to go into the intent log unless msync(2) is
used on the mapping with the MS_SYNC option.
You can't count on any writes to mmap(2)ed files hitting disk until
you msync(2) with MS_SYNC.  The system should want to wait as long as
possible before committing any mmap(2)ed file writes to disk.
Conversely you can't expect that no writes will hit disk until you
msync(2) or munmap(2).
Driven by fsflush which will scan memory (in chunks) looking for dirty,
unlocked, non-kernel pages to flush to disk.

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