On Fri 20 Jan 2023 at 12:41, Pablo Neira Ayuso <pablo@xxxxxxxxxxxxx> wrote: > Hi Vlad, > > On Thu, Jan 19, 2023 at 08:51:01PM +0100, Vlad Buslov wrote: >> Following patches in series need to update flowtable rule several times >> during its lifetime in order to synchronize hardware offload with actual ct >> status. However, reusing existing 'refresh' logic in act_ct would cause >> data path to potentially schedule significant amount of spurious tasks in >> 'add' workqueue since it is executed per-packet. Instead, introduce a new >> flow 'update' flag and use it to schedule async flow refresh in flowtable >> gc which will only be executed once per gc iteration. > > So the idea is to use a NF_FLOW_HW_UPDATE which triggers the update > from the garbage collector. I understand the motivation here is to > avoid adding more work to the workqueue, by simply letting the gc > thread pick up for the update. > > I already proposed in the last year alternative approaches to improve > the workqueue logic, including cancelation of useless work. For > example, cancel a flying "add" work if "delete" just arrive and the > work is still sitting in the queue. Same approach could be use for > this update logic, ie. cancel an add UDP unidirectional or upgrade it > to bidirectional if, by the time we see traffic in both directions, > then work is still sitting in the queue. Thanks for the suggestion. I'll try to make this work over regular workqueues without further extending the flow flags and/or putting more stuff into gc. > > I am sorry to say but it seems to me this approach based on flags is > pushing the existing design to the limit. The flag semantics is > already overloaded that this just makes the state machine behind the > flag logic more complicated. I really think we should explore for > better strategies for the offload work to be processed. Got it.
