Re: [PATCH v3 0/4] irqfd, iothread and polling support

[Klaus Jensen]

On Aug 27 17:12, Jinhao Fan wrote:
> This series of performance enhancements brings iothread and polling
> capabilities to qemu-nvme. The first two patches implements support
> for irqfd, which solves thread safety problems for interrupt emulation
> outside the main loop thread. The third patch adds support for
> emulating NVMe IO queues in a dedicated iothread, which avoid
> interference from other devices running on the main loop thread.
> The fourth patch implements SQ and CQ pollers, thus enabling polling
> on SQ and CQ.
> 
> After all these optimizations, our performance becomes similar to
> virtio-blk.
> 
> Comparison (KIOPS):
> 
> QD                    1   4  16  64
> virtio-blk           59 185 260 256
> nvme                 53 155 245 309
> virtio-blk-polling   88 212 210 213
> nvme-polling        123 165 189 191
> 

While reviewing this I noticed that the commit that introduced the
ioeventfd, we end up disabling batching of cqes (that is, we post and
interrupt for *each* cqe).

I'll post a patch to rectify that. With that, I am seeing progressive
performance improvements with the patches in this series.

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