Re: ext3_ordered_writepage() questions

[Stephen C. Tweedie]

Hi,

On Fri, 2006-03-17 at 15:23 -0800, Mingming Cao wrote:

> > > There is one other perspective to be aware of, though: the current
> > > behaviour means that by default ext3 generally starts flushing pending
> > > writeback data within 5 seconds of a write.  Without that, we may end up
> > > accumulating a lot more dirty data in memory, shifting the task of write
> > > throttling from the filesystem to the VM.  

> Current data=writeback mode already behaves like this, so the VM
> subsystem should be tested for a certain extent, isn't?

Yes, but there are repeated reports that for many workloads,
data=writeback is actually slower than data=ordered.  So there are
probably some interactions like this which may be hurting us already.

--Stephen


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