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Re: [GOLD] add new method for computing a build ID


From: Geoff Pike <gpike@chromium.org>
Date: Wed, 3 Oct 2012 12:35:48 -0700

>>> Motivation for the change: computing a build ID is currently a
>>> sequential bottleneck. E.g., in the example I mentioned in my email
>>> yesterday, a 24.5s link was spending 5.2s on the build ID computation.
>>
>> Have you tried linking with OpenSSL and using their optimized MD5 and
>> SHA1 variants?  I bet it makes a huge difference, some cpus even have
>> SHA1 and MD5 instructions.
>>
>> For example, on my machine we can SHA1 at a rate of 760MB/sec and
>> MD5 at a rate of ~775MB/sec.
> 
> I thought about trying a faster version of what's already being done,
> but felt that should be a lower priority than getting rid of the
> sequential bottleneck.

At the cost of needlessly making the hash weaker?  That sounds like
a terrible tradeoff, especially if it is found to be completely
unnecessary after doing the experiements I suggested above.


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