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Re: Speed-optimized file copy
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Re: Speed-optimized file copy


  • Subject: Re: Speed-optimized file copy
  • From: email@hidden
  • Date: Tue, 19 Jul 2011 19:22:52 -0500

On Tue, 19 Jul 2011 10:38:11 -0700, Wim Lewis wrote:
On 18 Jul 2011, at 1:25 PM, Stevo Brock wrote:
The idea is that with 4 concurrent operations executing, the
OS is getting fed a lot of disk operation requests such that
it can reorder the requests to maximize file system efficiency.
The deployment is OS X 10.6 minimum so we can use any tech available.


What are ways that we could improve the efficiency of this system?

I haven't tested on Darwin, but on some systems you can get a significant efficiency improvement using the aio_* interface (POSIX asynchronous IO). Not only does this let the kernel see multiple outstanding requests and retire them out-of-order, but the particular semantics of aio require less work from the VM system to guarantee correctness. Darwin's different, presumably, but it might be worth looking into.

This is interesting.

I wonder how many simultaneous requests one can make before the performance improvements (if there are any on Mac OS X) would disappear when using AIO...




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References: 
 >Speed-optimized file copy (From: Stevo Brock <email@hidden>)
 >Re: Speed-optimized file copy (From: Wim Lewis <email@hidden>)

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