Hi Honnappa, Thanks a lot for the detailed explanation. So I assume there has been a plan to improve the linux generic timer and I can also expect the hardware timer implementation.
For the question you mention, please check below information about out project: 1. it is multicore network firewall which targets on running on Intel X86 (with DPDK)/Cavium ARM (with Octeon NP hardware support) platform. It also can run on VM environment with ODP DPDK support. 2. the core number is variable depends on different platform, from 2 worker cores to 32+ worker cores. And of course, it will be nice I can help to put more thought and practice on the improvement of timer system. Best Regards, Mario -----Original Message----- From: Honnappa Nagarahalli [mailto:[email protected]] Sent: 2017年4月8日 1:13 To: Bill Fischofer <[email protected]> Cc: Mario (Miao) Mao <[email protected]>; Zhong Chen <[email protected]>; [email protected] Subject: Re: [lng-odp] linux-gen: timer: ODP general timer timeout machenism on massive timers usage On 7 April 2017 at 10:33, Bill Fischofer <[email protected]> wrote: > Thanks for your note Mario. As an aside, please subscribe to the ODP > mailing list otherwise I have to approve each post you make manually, > which will only add delay. Please see > https://lists.linaro.org/mailman/listinfo/lng-odp for that. We also > have a weekly public call on Tuesdays at 15:00 UTC (that's 8:00AM > PDT). Just go do http://meetings.opendataplane.org to join us. > > > On Fri, Apr 7, 2017 at 3:24 AM, Mario (Miao) Mao <[email protected]> wrote: >> Hi All, >> >> We have a project to adapt an existed firewall implementation to ODP >> framework. The current implementation needs to generate massive number of >> timer which link to each flow element. So there is requirement to run up to >> a million of timers to trigger the flow event. >> Definitely a very good problem to solve for timer implementation in ODP. Currently we are working on improving the timer implementation. Please take a look at the presentation I made at BUD17: http://connect.linaro.org/resource/bud17/bud17-320/. It talks about the current state, how the problem can be divided and the work we are doing to address some parts of the issue. >> An straightforward solution for us is to directly use ODP timer API to do >> the adaption. So we need to create individual timer for each flow element >> and attach a timeout event on. The advantage is the ODP event scheduling >> queue mechanism can help on a lockless flow processing for timeout event >> will be placed intp the same queue with packet belong to this flow. The >> prototype of this solution does work and it perfect fit our original >> processing flow. >> >> However, by carefully checking the ODP timer trigger mechanism, we find >> there could be performance issue when massive flow timer is created. The >> reason is current ODP timer implementation seems to run a full loop to check >> all active timers, regardless whether the timer will timeout in coming tick. >> So the worst situation is the timer_thread needs to check a million of timer >> tick buffer entries in each resolution interval. I do worry about it >> impacting the system performance or causing timer event losing. > > odp-linux is a general reference implementation designed for clarity > rather than performance. Since ODP supports multiple implementations, > the expectation is that each platform will provide a conforming > implementation that is optimized to it. For example, on platforms that > have a dedicated hardware timer engine the ODP APIs would be mapped > directly to that hardware by the implementation. > > For general production-grade operation we are developing an odp-cloud > implementation that is intended to be far more scalable and efficient. > You're welcome to participate in that definition/development. > >> >> So by a general thought, is that a better way to distribute active timer >> entries to different tick buckets instead of putting in a large tick buffer >> pool? In each resolution interval, the timer system only checks expired tick >> bucket and flush timeout events attached to expired timers. In an example of >> setting resolution to 1/10 second and allowing up to 120 second relative >> timeout, a bucket table (size = 1200) is needed and the loop round could be >> reduced to 1/1200 comparing of current mechanism. The only trade off is a >> tick bucket table which need more memory plus a complex timer adding/reset >> algorithm comparing with current one. > > That may be a promising approach and sounds similar to the work > currently ongoing on providing an optimized scalable software > scheduler intended to be one of the centerpieces of odp-cloud. Please > feel free to develop these thoughts further and join us to help > realize them. > This is one of the parts that was on our road-map to optimize. Can you provide more information about your system? Can I assume that it is a multi-core general CPU kind of environment? How many cores do you expect in the system? >> >> Let me know if I make some misunderstanding on current implementation. And >> thanks a lot for any comments. >> >> Mario Mao >> Software Engineer >> SonicWALL >> office +86 21 65100909 Ext: 42415 >>
