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From: Paul Hemmer <paulhemmer@hotmail.com>
To: Bob Friesenhahn <bfriesen@simple.dallas.tx.us>
Thread-Topic: [Tiff] Strategies for multi-core speedups
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Cc: Larry Gritz <lg@larrygritz.com>,
	"tiff@lists.maptools.org" <tiff@lists.maptools.org>
Subject: Re: [Tiff] Strategies for multi-core speedups
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Very interesting to read this discussion!

> On Jan 15, 2018, at 7:30 PM, Bob Friesenhahn <bfriesen@simple.dallas.tx.us> wrote:
> 
>> On Mon, 15 Jan 2018, Larry Gritz wrote:
>> 
>> There is no mystery here -- the I/O itself is still serialized, so 
>> if it's only 10% of the total runtime, say, even perfectly linear 
>> thread scaling and an unlimited number of cores without any lock 
>> contention will experience a maximum of 10x improvement. Amdahl's 
>> Law and all that. That effect alone adequately explains my lack of 
>> thread scalability beyond 8 or so cores, for this application.
> 
> The I/O is not necessarily serialized.  When using mmap, pread/pwrite, 
> or asynchronous I/O, the I/O can also benefit from multi-threading 
> given that the underlying storage is a multi-disk array or SSDs using 
> PCIe NVMe (capable of up to 1024 simultaneous I/Os).
> 
> Amdahl's Law still applies. :-)
> 
> Bob
> -- 
> Bob Friesenhahn
> bfriesen@simple.dallas.tx.us, https://eur03.safelinks.protection.outlook.com/?url=http%3A%2F%2Fwww.simplesystems.org%2Fusers%2Fbfriesen%2F&data=02%7C01%7C%7C884284da4ded44509cae08d55c784a86%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C636516594072892406&sdata=anY9qhnjanVD%2FcBa0OQ2eAy76wUG%2FfmfgJG86ius0ug%3D&reserved=0
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