On Fri, Jun 02, 2023 at 03:32:26PM +0200, Peter-Jan Gootzen wrote: > When the Virtio queue is full, a work item is scheduled > to execute in 1ms that retries adding the request to the queue. > This is a large amount of time on the scale on which a > virtio-fs device can operate. When using a DPU this is around > 40us baseline without going to a remote server (4k, QD=1). > This patch queues requests when the Virtio queue is full, > and when a completed request is taken off, immediately fills > it back up with queued requests. > > This reduces the 99.9th percentile latencies in our tests by > 60x and slightly increases the overall throughput, when using a > queue depth 2x the size of the Virtio queue size, with a > DPU-powered virtio-fs device. > > Furthermore, the virtio-fs driver now also always lets -ENOMEM > errors go to userspace instead of retrying the request in the > driver. > > Signed-off-by: Peter-Jan Gootzen <peter-jan@xxxxxxxxxxx> > --- > V3: Fixed requests falling into the void when -ENOMEM and no new > incoming requests. Virtio-fs now always lets -ENOMEM bubble up to > userspace. Also made queue full condition more explicit with > -ENOSPC in `send_forget_request`. > V2: Not scheduling dispatch work anymore when not needed > and changed delayed_work structs to work_struct structs Hi Peter-Jan, I will be traveling and will try to look at this patch as soon as possible. If Vivek and others are happy, please don't wait for me. Thanks, Stefan
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