On 10/6/15, 1:11 PM, Eric W. Biederman wrote: > ebied...@xmission.com (Eric W. Biederman) writes: > >> Roopa Prabhu <ro...@cumulusnetworks.com> writes: >> >>> From: Roopa Prabhu <ro...@cumulusnetworks.com> >>> >>> This patch adds support for MPLS multipath routes. >>> >>> Includes following changes to support multipath: >>> - splits struct mpls_route into 'struct mpls_route + struct mpls_nh' >>> >>> - 'struct mpls_nh' represents a mpls nexthop label forwarding entry >>> >>> - moves mpls route and nexthop structures into internal.h >>> >>> - A mpls_route can point to multiple mpls_nh structs >>> >>> - the nexthops are maintained as a list >> So I am not certain I like nexthops being a list. In the practical case >> introducing this list guarantees that everyone will see at least an >> extra cache line miss in the forwarding path. >> >> In the more abstract sense a list is the wrong data structure. If the >> list is so short we can afford to walk it an array is a better data >> structure. If we need enough entries to make the memory consumption >> of an array a concern we want some kind of hash table or tree data >> structure, because a list will be too long in that case. >> >> So can we please not use a list? >> >> I expect we can simplify the data structures by noting that rt_via must >> be an ethernet mac today so that 6 bytes are enough and 8 bytes gives us >> a bit extra and aligns things nicely. > Grr. My mistake. The current worst case is 16 bytes for an ipv6 > address in rt_via. But the point remains that a fixed sized array of > bytes in rt_via allows the use of an array and not a list for nexthops. > > At least for the single nexthop case I really want something that is > small enough it fits in a single 64byte cache line. The performance > compared to anything else is going to be noticable. > agree. Just responded to your last email. I moved from array to list only because of the extra bytes. I would prefer an array too.
http://marc.info/?l=linux-netdev&m=143932956719398&w=2 or https://patchwork.ozlabs.org/patch/506226/ link to full series is here: http://marc.info/?l=linux-netdev&m=143932955919395&w=2 thanks, Roopa -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
