Re: Crash soon after an alloc_skb failure in 2.6.16 and previous,swap disabled

From: Just Marc
Date: Thu Mar 30 2006 - 13:41:15 EST


Hi
I'm running a few machines with swap turned off and am experiencing
crashes when the system is extremely low on kernel memory. So far the
crashes observed are always inside the recv function of the Ethernet
[SNIPPED...]

Huh? If no buffers are available, received packets get thrown on the
floor. I see the failure(s) happened in an interrupt. If so, the
problem is in the network driver and your starved memory situation
brought out a bug.

The printout to the kernel log I attached to the previous email still does not mean the crash occurred there and then.
The benefits of running a system without swap are arguable, but in my
particular scenario I prefer to have connections dropped rather than
experience the overheads and latencies of a heavily swapping system.

I read this as; "I want the advantages of swap, but I don't want
to use swap." Or, "It doesn't work as I expected so therefore it's
broken!" In any event, swap is used to handle the problems with a
finite amount of memory. Normally sleeping tasks get swapped out,
freeing their memory for your network stuff. If you don't have swap,
that memory can't be freed. Tough! You did it, so you live with
it -- but contact the maintainer of your network card. You may
have forced a bug to come to the surface.

In most cases you are right, in my case, there is almost no application used RAM and therefore nothing to be freed. In my particular case I don't *really* need memory freed, I know a little odd.

But, as this is issue is occurring with at least e1000 and tg3 the bug might not be in these particular drivers. As I do not have a crash dump or log of what happened when the system froze, I have no way of knowing.

As this problem is easily reproducible, I'll leave it to the kernel people involved to dig into it, that is of course, if they are interested.

Thanks
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