Stephen Hemminger wrote, On 04/24/2009 06:18 PM: > On Fri, 24 Apr 2009 06:58:39 +0200 > Eric Dumazet <dada1@xxxxxxxxxxxxx> wrote: > >> Stephen Hemminger a écrit : >>> In days of old in 2.6.29, netfilter did locketh using a >>> lock of the reader kind when doing its table business, and do >>> a writer when with pen in hand like a overworked accountant >>> did replace the tables. This sucketh and caused the single >>> lock to fly back and forth like a poor errant boy. >>> >>> But then netfilter was blessed with RCU and the performance >>> was divine, but alas there were those that suffered for >>> trying to replace their many rules one at a time. >>> >>> So now RCU must be vanquished from the scene, and better >>> chastity belts be placed upon this valuable asset most dear. >>> The locks that were but one are now replaced by one per suitor. >>> >>> The repair was made after much discussion involving >>> Eric the wise, and Linus the foul. With flowers springing >>> up amid the thorns some peace has finally prevailed and >>> all is soothed. This patch and purple prose was penned by >>> in honor of "Talk like Shakespeare" day. >>> >>> Signed-off-by: Stephen Hemminger <shemminger@xxxxxxxxxx> >> >> Philip Davis of the university’s School of English said : >> >> "Shakespeare surprises the brain and catches it off guard in >> a manner that produces a sudden burst of activity - a sense >> of drama created out of the simplest of things." >> >> http://www.physorg.com/news85664210.html >> >>> --- >>> What hath changed over the last two setting suns: >>> * more words, mostly correct... >>> >>> * no need to locketh for writeh on current cpu tis >>> always so >>> >>> * the locking of all cpu's on replace is always done as >>> part of the get_counters cycle, so the sychronize swip >>> in replace tables is gone with only a comment remaing >>> >>> include/linux/netfilter/x_tables.h | 55 ++++++++++++++-- >>> net/ipv4/netfilter/arp_tables.c | 125 ++++++++++-------------------------- >>> net/ipv4/netfilter/ip_tables.c | 126 ++++++++++--------------------------- >>> net/ipv6/netfilter/ip6_tables.c | 123 ++++++++++-------------------------- >>> net/netfilter/x_tables.c | 55 ++++++++-------- >>> 5 files changed, 188 insertions(+), 296 deletions(-) >>> >> >>> >>> static int __init xt_init(void) >>> { >>> - int i, rv; >>> + unsigned int i; >>> + int rv; >>> + static struct lock_class_key xt_lock_key[NR_CPUS]; >> Could we avoid this [NR_CPUS] thing ? >> >>> + >>> + for_each_possible_cpu(i) { >>> + rwlock_t *lock = &per_cpu(xt_info_locks, i); >>> + >>> + rwlock_init(lock); >>> + lockdep_set_class(lock, xt_lock_key+i); >>> + } >> >> Did you tried : >> >> static DECLARE_PER_CPU(struct lock_class_key, xt_locks_key); >> > > The lock keys are really only used by lock dep, and I thought per cpu > space was more scarce on some arch. > Maybe I'm wrong but after this change: "- only acquire one cpu write lock at a time" lockdep_set_class() might be unnecessary. Alas I'm not able to test it. Jarek P. -- To unsubscribe from this list: send the line "unsubscribe netfilter-devel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
