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Date: Tue, 03 Jan 2012 14:37:57 +0100 From: Eric Dumazet <eric.dumazet@...il.com> To: David Laight <David.Laight@...LAB.COM> Cc: pablo@...filter.org, netfilter-devel@...r.kernel.org, davem@...emloft.net, netdev@...r.kernel.org Subject: RE: [PATCH 06/19] netfilter: nf_conntrack: use atomic64 for accounting counters Le mardi 03 janvier 2012 à 14:31 +0100, Eric Dumazet a écrit : > Le mardi 03 janvier 2012 à 12:01 +0000, David Laight a écrit : > > > if (acct) { > > > - spin_lock_bh(&ct->lock); > > > - acct[CTINFO2DIR(ctinfo)].packets++; > > > - acct[CTINFO2DIR(ctinfo)].bytes += skb->len; > > > - spin_unlock_bh(&ct->lock); > > > + atomic64_inc(&acct[CTINFO2DIR(ctinfo)].packets); > > > + atomic64_add(skb->len, > > &acct[CTINFO2DIR(ctinfo)].bytes); > > > } > > > > On a 32bit arch the two atomic64 operations require a locked > > bus cycle each. The spin_unlock_bh() may not need one - so > > the code may now be slower (modulo lock contention etc). > > > > Probably worth caching &acct[CTINFO2DIR(ctinfo)] in a local, > > the compiler probably can't do it itself. > > You're mistaken. > > Compile a UP kernel and check yourself before doing such claims. > > Oops sorry, I misread your mail, I thought you were speaking of UP kernel. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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