Ravikiran G Thirumalai <[EMAIL PROTECTED]> wrote: > > On Thu, Feb 02, 2006 at 07:16:00PM -0800, Andrew Morton wrote: > > Ravikiran G Thirumalai <[EMAIL PROTECTED]> wrote: > > > > > > On Fri, Jan 27, 2006 at 03:01:06PM -0800, Andrew Morton wrote: > > > Here's an implementation which delegates tuning of batching to the user. > > > We > > > don't really need local_t at all as percpu_counter_mod is not safe against > > > interrupts and softirqs as it is. If we have a counter which could be > > > modified in process context and irq/bh context, we just have to use a > > > wrapper like percpu_counter_mod_bh which will just disable and enable > > > bottom > > > halves. Reads on the counters are safe as they are atomic_reads, and the > > > cpu local variables are always accessed by that cpu only. > > > > > > (PS: the maxerr for ext2/ext3 is just guesstimate) > > > > Well that's the problem. We need to choose production-quality values for > > use in there. > > The guesstimate was loosely based on keeping the per-cpu batch at atleast 8 > on reasonably sized systems, while not letting maxerr grow too big. I guess > machines with cpu counts more than 128 don't use ext3 :). And if they do, > they can tune the counters with a higher maxerr. I guess it might be a bit > ugly on the user side with all the if num_possibl_cpus(), but is there a > better alternative? > > (I plan to test the counter values for ext2 and ext3 on a 16 way box, and > change these if they turn out to be not so good)
OK, thanks. Frankly I think I went overboard on the scalability thing when adding percpu counters to ext2 and ext3. I suspect they're not providing significant benefit over per-sb-spinlock and a ulong. > > > > > Comments? > > > > Using num_possible_cpus() in that header file is just asking for build > > errors. Probably best to uninline the function rather than adding the > > needed include of cpumask.h. > > Yup, > > Here it is. > > Change the percpu_counter interface so that user can specify the maximum > tolerable deviation. OK, thanks. I need to sit down and a) remember why we're even discussing this and b) see what we've merged thus far and work out what it all does ;) - 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
