Le 8 nov. 2012 à 11:25, Alexander V. Chernikov a écrit : > On 08.11.2012 14:24, Andre Oppermann wrote: >> On 08.11.2012 00:24, Alexander V. Chernikov wrote: >>> Hello list! >>> >>> Currently we need to acquire 2 read locks to perform simple 6-byte >>> copying from arp record to packet >>> ethernet header. >>> >>> It seems that acquiring lle lock for fast path (main traffic flow) is >>> not necessary even with >>> current code. >>> >>> My tests shows ~10% improvement with this patch applied. >>> >>> If nobody objects I plan to commit this change at the end of next week. >> >> This is risky and prone to race conditions. The copy of the MAC address >> should be done while the table read lock is held to protect against the > It is done exactly as you say: table read lock is held.
How do you protect from entry update if i've a ref to the entry ? You can end up doing bcopy of a partial mac address. la_preempt modification is also write access to an unlocked structure. > >> entry going away. You can either return with table lock held and drop >> it after the copy, or you could a modified lookup function that takes a >> pointer for the copy destination, do the copy with the read lock, and then >> return. If no entry is found an error is returned and obviously no copy >> is done. >> > > > -- > WBR, Alexander > > > _______________________________________________ > freebsd-hackers@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-hackers > To unsubscribe, send any mail to "freebsd-hackers-unsubscr...@freebsd.org" _______________________________________________ freebsd-hackers@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-hackers To unsubscribe, send any mail to "freebsd-hackers-unsubscr...@freebsd.org"
