On Oct 30, 2014, at 3:38 PM, Ben Pfaff <b...@nicira.com> wrote: > On Tue, Oct 28, 2014 at 07:05:01PM -0700, Jarno Rajahalme wrote: >> >>> On Oct 28, 2014, at 4:36 PM, Ben Pfaff <b...@nicira.com> wrote: >>> >>>> On Fri, Oct 24, 2014 at 01:36:40PM -0700, Jarno Rajahalme wrote: >>>> Previously, accurate iteration required writers to be excluded during >>>> iteration. This patch changes the structure of the classifier by >>>> moving the list of rules from struct cls_match to struct cls_subtable. >>>> The list element is also moved from the struct cls_match to struct >>>> cls_rule, which makes iteration more straightforward, and allows the >>>> iterators to remain ignorant of the internals of the cls_match. These >>>> changes allow iteration of rules in the classifier by traversing the >>>> RCU-friendly subtables vector, and the rculist of rules in each >>>> subtable. Classifier modifications may be performed concurrently, but >>>> whether or not the concurrent iterator sees those changes depends on >>>> the timing of change. This is similar to having writers excluded by a >>>> mutex, where visibility of changes depends on the timing of mutex >>>> acquisition. >>>> >>>> The subtable's rculist also allows to make >>>> classifier_find_rule_exactly() and classifier_rule_overlaps() >>>> lockless. >>>> >>>> Signed-off-by: Jarno Rajahalme <jrajaha...@nicira.com> >>> >>> I *think* I follow what's going on here, but just to be sure, let me >>> try to explain it. After this patch, the subtable has a list of every >>> rule in the subtable, as 'rules_list'. The rules in the list are in >>> no particular order, except that rules with identical match criteria >>> are in subsequent positions. Is that correct? >> >> Yes :-) > > The conjunctive match series uses the list of lower-priority rules in > lookup. I think that this patch, as-is, would make that a lot more > expensive, because it's no longer cheap to tell whether the next rule > in the list has the same match. I guess one could still mark > boundaries somehow; do you have an idea?
Will have to think about this. However, I totally missed this in my review of the conjunctive match; as the lower-priority rules list is not yet RCU, it cannot be safely used on lookups. It should be sufficient to convert from struct list in struct cls_match to struct rculist, tough. Jarno _______________________________________________ dev mailing list dev@openvswitch.org http://openvswitch.org/mailman/listinfo/dev
