On Wed, Jun 20, 2007 at 11:20:59AM +0200, Jens Axboe wrote: > On Wed, Jun 20 2007, Peter Zijlstra wrote: > > On Wed, 2007-06-20 at 11:14 +0200, Jens Axboe wrote: > > > On Wed, Jun 20 2007, Andrew Morton wrote: > > > > Perhaps our queues are too long - if the VFS _does_ back off, it'll take > > > > some time for that to have an effect. > > > > > > > > Perhaps the fact that the queue size knows nothing about the _size_ of > > > > the > > > > requests in the queue is a problem. > > > > > > It's complicated, the size may not matter a lot. 128 sequential 512kb IO > > > may complete faster than 128 random 4kb IO's. > > > > Yes, is there any way a queue could be limited to a certain amount of > > 'completion time' ? > > Not easily, we'd need some sort of disk profile for that to be remotely > reliable.
Perhaps we want to throw some sliding window algorithms at it. We can bound requests and total I/O and if requests get retired too slowly we can shrink the windows. Alternately, we can grow the window if we're retiring things within our desired timeframe. -- Mathematics is the supreme nostalgia of our time. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
