Re: Linux 2.4.5-ac15

[Marcelo Tosatti]

On Thu, 21 Jun 2001, Mike Galbraith wrote:

> On Thu, 21 Jun 2001, Marcelo Tosatti wrote:
> 
> > >  2  4  2  77084   1524  18396  66904   0 1876   108  2220 2464 66079   198   1
>                                                                    ^^^^^
> > Ok, I suspect that GFP_BUFFER allocations are fucking up here (they can't
> > block on IO, so they loop insanely).
> 
> Why doesn't the VM hang the syncing of queued IO on these guys via
> wait_event or such instead of trying to just let the allocation fail?

Actually the VM should limit the amount of data being queued for _all_
kind of allocations.

The problem is the lack of a mechanism which allows us to account the
approximated amount of queued IO by the VM. (except for swap pages)

You can see it this way: To get free memory we're "polling" instead of
waiting on the IO completion of pages.

> (which seems to me will only cause the allocation to be resubmitted,
> effectively changing nothing but adding overhead) 

Yes.

> Does failing the allocation in fact accomplish more than what I'm
> (uhoh:) assuming?

No.

It sucks really badly.