On Thu, 07 Dec 2006 21:23:07 +0100 Eric Dumazet <[EMAIL PROTECTED]> wrote:
> Stephen Hemminger a écrit : > > The hard header cache is in the main output path, so using > > seqlock instead of reader/writer lock should reduce overhead. > > > > Nice work Stephen, I am very interested. > > Did you benchmarked it ? > > I ask because I think hh_refcnt frequent changes may defeat the gain you want > (ie avoiding cache line ping pongs between cpus). seqlock are definitly > better > than rwlock, but if we really keep cache lines shared. > > So I would suggest reordering fields of hh_cache and adding one > ____cacheline_aligned_in_smp to keep hh_refcnt in another cache line. > > (hh_len, hh_lock and hh_data should be placed on a 'mostly read' cache line) > > Thank you > Eric It doesn't make any visible performance difference for real networks; copies and device issues are much larger. The hh_refcnt is used only when creating destroying neighbor entries, so except under DoS attack it doesn't make a lot of difference. The hh_lock is used on each packet sent. - 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
