Re: [Virtio-fs] Achieving parallelism in virtiofsd

[piaojun <piaojun@huawei.com>]

Hi Stefan,

>From your description, virtiofsd does the same work as SPDK, and I
wonder if we could adapt it to SPDK-vhost-fs which is widely used.

Thanks,
Jun

On 2019/7/4 18:46, Stefan Hajnoczi wrote:
> Hi,
> Here are my plans for achieving parallelism in virtiofsd.  This will
> improve performance for workloads that keep more than one request in
> flight at a time.
> 
> Today virtiofsd performance is limited because it only processes 1
> request at a time.  This can be improved in two independent ways:
> parallel request processing and multiqueue.
> 
> Parallel request processing means working on more than one request at a
> time.  A request that blocks should not prevent the next request from
> executing.  The FUSE protocol is asynchronous so it's just a question of
> adjusting virtiofsd.
> 
> Multiqueue means providing several request virtqueues instead of just
> one.  This can be used with CPU and NUMA pinning so that request
> processing takes place on a core and NUMA node.  Better locality can
> result in higher performance.
> 
> virtiofsd needs to offer both of these features.  The model I'm
> proposing is one thread per virtqueue which distributes requests to a
> thread pool for execution.  Each virtqueue thread and its thread pool
> can be bound to a subset of CPUs.
> 
> Separate optimizations such as virtqueue polling could be added later to
> reduce latency.
> 
> I plan to use the glib thread pool, which offers the basic functionality
> that virtiofsd requires.  In the process of this work I will also audit
> and fix passthrough_ll.c's thread-safety.
> 
> Feedback is appreciated!
> 
> Stefan
> 
> 
> 
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