From: Andi Kleen <[EMAIL PROTECTED]> Date: Sun, 4 Nov 2007 00:18:14 +0100
> On Thursday 01 November 2007 11:16:20 Eric Dumazet wrote: > > Some quick comments: > > > +#if defined(CONFIG_SMP) || defined(CONFIG_PROVE_LOCKING) > > +/* > > + * Instead of using one rwlock for each inet_ehash_bucket, we use a table > > of locks > > + * The size of this table is a power of two and depends on the number of > > CPUS. > > + */ > > This shouldn't be hard coded based on NR_CPUS, but be done on runtime > based on num_possible_cpus(). This is better for kernels with a large > NR_CPUS, but which typically run on much smaller systems (like > distribution kernels) I think this is a good idea. Eric, could you make this change? > Also the EHASH_LOCK_SZ == 0 special case is a little strange. Why did > you add that? He explained this in another reply, because ifdefs are ugly. > And as a unrelated node have you tried converting the rwlocks > into normal spinlocks? spinlocks should be somewhat cheaper > because they have less cache protocol overhead and with > the huge thash tables in Linux the chain walks should be short > anyways so not doing this in parallel is probably not a big issue. > At some point I also had a crazy idea of using a special locking > scheme that special cases the common case that a hash chain > has only one member and doesn't take a look for that at all. I agree. There was movement at one point to get rid of all rwlock's in the kernel, I personally think they are pointless. Any use that makes "sense" is a case where the code should be rewritten to decrease the lock hold time or convert to RCU. - 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
