On Fri 15 May 2020 at 20:25, David Miller <da...@davemloft.net> wrote: > From: Vlad Buslov <vla...@mellanox.com> > Date: Fri, 15 May 2020 14:40:10 +0300 > >> Output rate of current upstream kernel TC filter dump implementation if >> relatively low (~100k rules/sec depending on configuration). This >> constraint impacts performance of software switch implementation that >> rely on TC for their datapath implementation and periodically call TC >> filter dump to update rules stats. Moreover, TC filter dump output a lot >> of static data that don't change during the filter lifecycle (filter >> key, specific action details, etc.) which constitutes significant >> portion of payload on resulting netlink packets and increases amount of >> syscalls necessary to dump all filters on particular Qdisc. In order to >> significantly improve filter dump rate this patch sets implement new >> mode of TC filter dump operation named "terse dump" mode. In this mode >> only parameters necessary to identify the filter (handle, action cookie, >> etc.) and data that can change during filter lifecycle (filter flags, >> action stats, etc.) are preserved in dump output while everything else >> is omitted. >> >> Userspace API is implemented using new TCA_DUMP_FLAGS tlv with only >> available flag value TCA_DUMP_FLAGS_TERSE. Internally, new API requires >> individual classifier support (new tcf_proto_ops->terse_dump() >> callback). Support for action terse dump is implemented in act API and >> don't require changing individual action implementations. > ... > > This looks fine, so series applied. > > But really if people just want an efficient stats dump there is probably > a better way to efficiently encode just the IDs and STATs. Maybe even > put the stats in pages that userland can mmap() and avoid all of this > system call overhead and locking altogether.
Thanks! Adding such API will be my next step, if terse dump performance proves insufficient.
