Subject: Re: i/o scheduling (was Re: NEW_BUFQ_STRATEGY)
To: None <email@example.com>
From: YAMAMOTO Takashi <firstname.lastname@example.org>
Date: 12/18/2003 07:50:37
> > I must not understand what you're saying. You say "synchronous read
> > requests can happen on the delayed-writed page and we have no way to
> > look up the corresponding buf from a page". That suggests to me that
> > the read will return the wrong data; am I incorrect? If not, what is
> > the problem, exactly, if synchronous read requests happen on pages
> > that have delayed writes in the I/O queues?
> I'm not sure what all the hubub is all about ... don't all file data
> requests go through UBC in any case?
did you read my replies to tls@ and bouyer@? weren't them enough?
or am i missing the point?
my understanding is,
- page is PG_BUSY during write back. if we keep a delayed write
request at buffer queue forever, the page will be left PG_BUSY forever.
- getpages will wait on the PG_BUSY page.