Re: [RFC][DATA] re "ongoing vm suckage"

[Marcelo Tosatti <marcelo@conectiva.com.br>]

On Fri, 3 Aug 2001, Linus Torvalds wrote:

> 
> On Sat, 4 Aug 2001, Ben LaHaise wrote:
> >
> > Within reason.  I'm actually heading to bed now, so it'll have to wait
> > until tomorrow, but it is fairly trivial to reproduce by dd'ing to an 8GB
> > non-sparse file.  Also, duplicating a huge file will show similar
> > breakdown under load.
> 
> Well, I've made a 2.4.8-pre4.
> 
> This one has marcelo's zone fixes, and my request suggestions. I'm writing
> email right now with the 8GB write in the background, and unpacked and
> patched a kernel. It's certainly not _fast_, but it's not too painful to
> use either.  The 8GB file took 7:25 to write (including the sync), which
> averages out to 18+MB/s. Which is, as far as I can tell, about the best I
> can get on this 5400RPM 80GB drive with the current IDE driver (the
> experimental IDE driver is supposed to do better, but that's not for
> 2.4.x)
> 
> An added advantage of doing the waiting in the request handling was that
> this way it automatically balances reads against writes - writes cannot
> cause reads to fail because they have separate request queue allocations.
> 
> Does it work reasonably under your loads?

Well, the freepages_high change needs more work.

Normal allocations are not going to easily "fall down" to lower zones
because the high zones will be kept at freepages.high most of the time.