Messages in this thread | | | Date | Mon, 30 Sep 2002 00:45:59 +0530 | From | Dipankar Sarma <> | Subject | Re: [patch] smptimers, old BH removal, tq-cleanup, 2.5.39 |
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Hi Ingo,
First of all, YES! I am going to start testing first thing tomorrow.
On Sun, Sep 29, 2002 at 07:52:17PM +0200, Ingo Molnar wrote: > > i've done the following cleanups/simplifications to task-queues: > > - removed the ability to define your own task-queue, what can be done is > to schedule_task() a given task to keventd, and to flush all pending > tasks. > > this is actually a quite easy transition, since 90% of all task-queue > users in the kernel used BH_IMMEDIATE - which is very similar in > functionality to keventd.
This is a problem I ran into in my "kill-BHs" project. I was wondering if callbacks executed through keventd might have significantly higher latency (and potential starvation) compared to IMMEDIATE_BH driven task-queues and that might break existing drivers. Is this not going to be an issue ?
> net_bh_lock: i have removed it, since it would synchronize to nothing. The > old protocol handlers should still run on UP, and on SMP the kernel prints > a warning upon use. Alexey, is this approach fine with you?
The cache line bouncing of global_bh_lock and net_bh_lock in run_timer_tasklet() show up in our profiles, so getting rid of them is a good thing (TM).
> scalable timers: i've further improved the patch ported to 2.5 by wli and > Dipankar. There is only one pending issue i can see, the question of > whether to migrate timers in mod_timer() or not. I'm quite convinced that > they should be migrated, but i might be wrong. It's a 10 lines change to > switch between migrating and non-migrating timers, we can do performance > tests later on. The current, more complex migration code is pretty fast > and has been stable under extremely high networking loads in the past 2 > years, so we can immediately switch to the simpler variant if someone > proves it improves performance. (I'd say if non-migrating timers improve > Apache performance on one of the bigger NUMA boxes then the point is > proven, no further though will be needed.)
I will start testing this patch and will try to get you some numbers. Thanks for taking this up.
Thanks -- Dipankar Sarma <dipankar@in.ibm.com> http://lse.sourceforge.net Linux Technology Center, IBM Software Lab, Bangalore, India. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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