What's the concern about setting irq thread's policy as SCHED_FIFO
Subsystems (2)
I am doing network performance test under suse11sp3 and intel 82599 nic,
Becasuse the softirq is out of schedule policy's control, so netserver thread couldn't always get 100% cpu usage, then packet dropped in kernel udp socket's receive queue.
In order to get a stable result, I did some patch in ixgbe driver and then use irq_thread instead of softirq to handle rx. It seems work well, but irq_thread's SCHED_FIFO schedule policy cause that when the cpu is limited, netserver couldn't work at all.
So I change the irq_thread's schedule policy from SCHED_FIFO to SCHED_NORMAL, then the irq_thread could share the cpu usage with netserver thread.
the question is:
What's the concrete reason about setting irq thread's policy as SCHED_FIFO?
Except the priority affecting the cpu usage, any function would be broken if irq thread change to SCHED_NORMAL?
Quoted 9 lines · Qin Chuanyu
I am doing network performance test under suse11sp3 and intel 82599 nic, Becasuse the softirq is out of schedule policy's control, so netserver thread couldn't always get 100% cpu usage, then packet dropped in kernel udp socket's receive queue.
In order to get a stable result, I did some patch in ixgbe driver and then use
irq_threadinstead of softirq to handle rx.
It seems work well, but irq_thread'sSCHED_FIFOschedule policy cause that when the cpu is limited, netserver couldn't work at all.
I cannot speak to any scheduling issues/questions, but can ask if you tried binding netserver to a CPU other than the one servicing the interrupts via the -T option on the netperf command line:
netperf -T <netperfCPU>,<netserverCPU> ...
http://www.netperf.org/svn/netperf2/trunk/doc/netperf.html#index-g_t_002dT_002c-Global-41
happy benchnmarking,
rick jones
Quoted 14 lines
So I change the irq_thread's schedule policy from
SCHED_FIFOtoSCHED_NORMAL, then theirq_threadcould share the cpu usage with netserver thread.the question is:
What's the concrete reason about setting irq thread's policy asSCHED_FIFO? Except the priority affecting the cpu usage, any function would be broken if irq thread change toSCHED_NORMAL?--
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Quoted 11 lines · Rick Jones
Quoted 9 lines · Qin Chuanyu
I am doing network performance test under suse11sp3 and intel 82599 nic, Becasuse the softirq is out of schedule policy's control, so netserver thread couldn't always get 100% cpu usage, then packet dropped in kernel udp socket's receive queue.
In order to get a stable result, I did some patch in ixgbe driver and then use
irq_threadinstead of softirq to handle rx.
It seems work well, but irq_thread'sSCHED_FIFOschedule policy cause that when the cpu is limited, netserver couldn't work at all.
Quoted 8 lines
I cannot speak to any scheduling issues/questions, but can ask if you tried binding netserver to a CPU other than the one servicing the interrupts via the -T option on the netperf command line:
netperf -T <netperfCPU>,<netserverCPU> ...
http://www.netperf.org/svn/netperf2/trunk/doc/netperf.html#index-g_t_002dT_002c-Global-41
Yes, I had done this try, the irq_thread and netserver worked well without competition after binding them separately. I also had tried this test case in kernel 3.10, and without binding irq_thread and netserver work well separately.
So, the question is:
3.10: irq_thread netserver good 3.0.93: irq_thread netserver bad(compete single cpu)
normal thread in both kernel version is OK.
There must be a schedule policy change lead to this difference. Could anyone give some hint?
Quoted 16 lines
happy benchnmarking,
rick jones
Quoted 11 lines
So I change the irq_thread's schedule policy from
SCHED_FIFOtoSCHED_NORMAL, then theirq_threadcould share the cpu usage with netserver thread.the question is:
What's the concrete reason about setting irq thread's policy asSCHED_FIFO?
Except the priority affecting the cpu usage, any function would be broken if irq thread change toSCHED_NORMAL?