On Fri, Jan 27, 2006 at 03:08:47PM -0800, Andrew Morton wrote: > Andrew Morton <[EMAIL PROTECTED]> wrote: > > > > Oh, and because vm_acct_memory() is counting a singleton object, it can use > > DEFINE_PER_CPU rather than alloc_percpu(), so it saves on a bit of kmalloc > > overhead. > > Actually, I don't think that's true. we're allocating a sizeof(long) with > kmalloc_node() so there shouldn't be memory wastage.
Oh yeah there is. Each dynamic per-cpu object would have been atleast (NR_CPUS * sizeof (void *) + num_cpus_possible * cacheline_size ). Now kmalloc_node will fall back on size-32 for allocation of long, so replace the cacheline_size above with 32 -- which then means dynamic per-cpu data are not on a cacheline boundary anymore (most modern cpus have 64byte/128 byte cache lines) which means per-cpu data could end up false shared.... Kiran - 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
