Re: i/o scheduling (was Re: NEW_BUFQ_STRATEGY)

On Wed, Dec 17, 2003 at 03:30:15PM +0900, YAMAMOTO Takashi wrote:
> > 
> > Why would these reads be generated?  If the write has not completed, is
> > it not the case that the page must still be dirty, and should thus still
> > be in the cache?
> 
> because the page is marked as PG_BUSY during delayed write,
> VOP_GETPAGES will wait on it.  we have no way to hurry
> the i/o in this case.
> 
> maybe distinguishing PG_BUSY-for-read and PG_BUSY-for-write can be
> an alternative solution?

Won't this also help avoid reads, period, when the I/O queues get lots
of writes backed up in them?  That seems like a very good thing.

-- 
 Thor Lancelot Simon	                                      [email protected]
   But as he knew no bad language, he had called him all the names of common
 objects that he could think of, and had screamed: "You lamp!  You towel!  You
 plate!" and so on.              --Sigmund Freud