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Re: [Qemu-devel] [PATCH 00/12] nbd improvements

From: Kevin Wolf
Subject: Re: [Qemu-devel] [PATCH 00/12] nbd improvements
Date: Fri, 09 Sep 2011 12:42:57 +0200
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:6.0) Gecko/20110816 Thunderbird/6.0

Am 09.09.2011 12:29, schrieb Paolo Bonzini:
> On 09/09/2011 11:00 AM, Kevin Wolf wrote:
>> There is anonther patch enabling AIO for NBD on the list [1], by
>> Nicholas Thomas (CCed), that lacked review so far. Can you guys please
>> review each others approach and then converge on a solution? I guess
>> Paolo's patches 1-7 can be applied in any case, probably causing minor
>> conflicts, but for the rest we need to decide which one to pick.
> Stefan also pointed me to Nicholas's patches yesterday.  I would go with 
> mine, if only because his work predates coroutines (at least the older 
> versions) and are much more complex.
> On the other hand, Nicholas's work includes timeout and reconnect.  I'm 
> not sure how complicated it is to include it in my series, but probably 
> not much.  With coroutines, preserving the list of outstanding I/O 
> requests is done implicitly by the CoMutex, so you basically have to 
> check errno for ECONNRESET and similar errors, reconnect, and retry 
> issuing the current request only.
> Timeout can be done with a QEMUTimer that shuts down the socket 
> (shutdown(2) I mean).  This triggers an EPIPE when writing, or a 
> zero-sized read when reading.  The timeout can be set every time the 
> coroutine is (re)entered, and reset before exiting nbd_co_readv/writev.
> What do you think?

I haven't really had a look at your patches yet (I hope to do so later
today), but from the patch descriptions I would think that indeed your
patches could be the better base for a converged series.

What I would like you and Nick to do is to see what is missing from your
series compared to his one (you describe a couple of things, but let's
see if Nick knows anything else) and to agree on the next steps. I think
that a possible way is to merge your series and do the other
improvements on top, but as I said I haven't really looked into the
details yet.


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