Messages in this thread | | | Subject | Re: [PATCH v3 0/3] genirq/vfio: Introduce update_irq_devid and optimize VFIO irq ops | From | luoben <> | Date | Tue, 20 Aug 2019 23:51:23 +0800 |
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在 2019/8/20 下午11:22, Alex Williamson 写道: > On Tue, 20 Aug 2019 12:03:50 +0800 > luoben <luoben@linux.alibaba.com> wrote: > >> 在 2019/8/20 上午4:51, Alex Williamson 写道: >>> On Thu, 15 Aug 2019 21:02:58 +0800 >>> Ben Luo <luoben@linux.alibaba.com> wrote: >>> >>>> Currently, VFIO takes a lot of free-then-request-irq actions whenever >>>> a VM (with device passthru via VFIO) sets irq affinity or mask/unmask >>>> irq. Those actions only change the cookie data of irqaction or even >>>> change nothing. The free-then-request-irq not only adds more latency, >>>> but also increases the risk of losing interrupt, which may lead to a >>>> VM hung forever in waiting for IO completion >>> What guest environment is generating this? Typically I don't see that >>> Windows or Linux guests bounce the interrupt configuration much. >>> Thanks, >>> >>> Alex >> By tracing centos5u8 on host, I found it keep masking and unmasking >> interrupt like this: >> >> [1566032533709879] index:28 irte_hi:000000010004a601 >> irte_lo:adb54bc000b98001 >> [1566032533711242] index:28 irte_hi:0000000000000000 >> irte_lo:0000000000000000 >> [1566032533711258] index:28 irte_hi:000000000004a601 >> irte_lo:00003fff00ac002d >> [1566032533711269] index:28 irte_hi:000000000004a601 >> irte_lo:00003fff00ac002d > [snip] >> "[1566032533720007]" is timestamp in μs, so centos5u8 tiggers 30+ irte >> modification within 10ms > Ok, that matches my understanding that only very old guests behave in > this manner. It's a curious case to optimize as RHEL5 is in extended > life-cycle support, with regular maintenance releases ending 2+ years > ago. Thanks, > > Alex
But repeatedly set interrupt affinity in a new version guest can also cause the problem.
Thanks,
Ben
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