Re: Kernel deadlock using nbd over acenic driver.

Steven Whitehouse (steve@gw.chygwyn.com)
Thu, 16 May 2002 17:35:43 +0100 (BST)


Hi,

>
> "Oliver Xymoron wrote:"
> > On Thu, 16 May 2002, Peter T. Breuer wrote:
> > > Any way of making sure that send_msg on the socket can always get the
> > > (known a priori) buffers it needs?
> >
> > Not at present. Note that we also need reservations on the receive side
> > for ACK handling which is "interesting".
>
> One thing at a time. What if there is a zone "ceiling" that we keep
> lowered exactly until it is time for the process that does the send_msg
> to run, when we raise the ceiling. (I don't know how this VM stuff
> works in detail inside - this is an invitation to list the objections).
> The scheduler could presumably be trained to muck with the ceilings
> according to flags on the process (task?) structs.
>
> Peter
>
Thats effectively what PF_MEMALLOC does. The code in question is in
page_alloc.c:__alloc_pages just before and after the rebalance: label.
The z->pages_min gives a per zone minimum for "other processes" that are
not PF_MEMALLOC,

Steve.

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