On Thu, 15 Dec 2005 18:09:22 -0800 Sridhar Samudrala <[EMAIL PROTECTED]> wrote:
> On Thu, 2005-12-15 at 00:21 -0800, David S. Miller wrote: > > From: Sridhar Samudrala <[EMAIL PROTECTED]> > > Date: Wed, 14 Dec 2005 23:37:37 -0800 (PST) > > > > > Instead, you seem to be suggesting in_emergency to be set dynamically > > > when we are about to run out of ATOMIC memory. Is this right? > > > > Not when we run out, but rather when we reach some low water mark, the > > "critical sockets" would still use GFP_ATOMIC memory but only > > "critical sockets" would be allowed to do so. > > > > But even this has faults, consider the IPSEC scenerio I mentioned, and > > this applies to any kind of encapsulation actually, even simple > > tunneling examples can be concocted which make the "critical socket" > > idea fail. > > > > The knee jerk reaction is "mark IPSEC's sockets critical, and mark the > > tunneling allocations critical, and... and..." well you have > > GFP_ATOMIC then my friend. > > I would like to mention another reason why we need to have a new > GFP_CRITICAL flag for an allocation request. When we are in emergency, > even the GFP_KERNEL allocations for a critical socket should not > sleep. This is because the swap device may have failed and we would > like to communicate this event to a management server over the > critical socket so that it can initiate the failover. > > We are not trying to solve swapping over network problem. It is much > simpler. The critical sockets are to be used only to send/receive > a few critical messages reliably during a short period of emergency. > If it is only one place, why not pre-allocate one "I'm sick now" skb and hold onto it. Any bigger solution seems to snowball into a huge mess. -- Stephen Hemminger <[EMAIL PROTECTED]> OSDL http://developer.osdl.org/~shemminger - To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
