On Thu, Aug 16, 2007 at 01:15:05PM +1000, Paul Mackerras wrote: > > But others can also reduce the reservation. Also, the code sets and > clears *sk->sk_prot->memory_pressure nonatomically with respect to the > reads of sk->sk_prot->memory_allocated, so in fact the code doesn't > guarantee any particular relationship between the two.
Yes others can reduce the reservation, but the point of this is that the code doesn't care. We'll either see the value before or after the reduction and in either case we'll do something sensible. The worst that can happen is when we're just below the hard limit and multiple CPUs fail to allocate but that's not really a problem because if the machine is making progress at all then we will eventually scale back and allow these allocations to succeed. As to the non-atomic operation on memory_pressue, that's OK because we only ever assign values to it and never do other operations such as += or -=. Remember that int/long assignments must be atomic or Linux won't run on your architecture. Cheers, -- Visit Openswan at http://www.openswan.org/ Email: Herbert Xu ~{PmV>HI~} <[EMAIL PROTECTED]> Home Page: http://gondor.apana.org.au/~herbert/ PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt - 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
