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List:       cyrus-info
Subject:    Re: cyrus-imap buildin: sse extention
From:       Anatoli <me () anatoli ! ws>
Date:       2020-06-29 3:15:57
Message-ID: 4108dd82-db6a-b652-b397-c7753f55604b () anatoli ! ws
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Ellie,

I also had the doubt about this feature, though I'd already seen a mention that the \
result of the hw implementation is incompatible (and before your last mail completely \
forgot about it).

Maybe it makes sense to remove its mention (and detection) from configure altogether, \
until it becomes useful? Just to not confuse those building it from sources.

Regards,
Anatoli

On 28/6/20 21:29, ellie timoney wrote:
> Hi Sergey,
> 
> > Hardware support:
> > SSE4.2:             yes
> 
> This is detected for a hardware implementation of the CRC32c algorithm.  Cyrus \
> doesn't actually use it though, because it's not compatible with the existing CRC32 \
> algorithm: i.e. for the same input, it produces a different checksum, which would \
> break everything on a system with pre-existing data. 
> If you _want_ to use the hardware CRC32c algorithm on a brand new deployment (and \
> know what you are doing), I believe at this stage you would need to patch Cyrus to \
> use it -- the code is there, but it is never called. 
> > Can Cyrus-IMAP be running on systems without SSE4 at this case?
> 
> Yep, it'll work just fine.  The hardware CRC32c code will simply not be compiled, \
> which, since it isn't used anyway, will have no effect. 
> > If no, can I set limit to SSE2 ?
> 
> There's currently no configurability for this at all.  I don't know if it's even \
> possible to implement the same algorithm with SSE2.  At the moment I assume that, \
> since it's looking for SSE42 specifically, then that means that the hardware \
> feature it needs is probably only available in SSE42. 
> Cheers,
> 
> ellie
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