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Subject: Re: [Qemu-devel] [PATCH 1/2] coroutine: introduce coroutines
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To: Anthony Liguori <anthony@codemonkey.ws>
Cc: Kevin Wolf <kwolf@redhat.com>, Anthony Liguori <aliguori@us.ibm.com>, Venkateswararao Jujjuri <jvrao@linux.vnet.ibm.com>, Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>, qemu-devel@nongnu.org

On 05/24/2011 11:21 PM, Anthony Liguori wrote:
> Why not use threads as a coroutine fallback?  That's essentially what we
> would do to be "fully threaded".

Not exactly, there would be much less synchronization going on.  Using 
threads to implement coroutines means you go through the slow path of 
the synchronization primitives (either mutexes/condvars or barriers) 
twice or more per coroutine switch.  It is really slow, a 100 times 
difference perhaps.

Paolo