As I've been slacking (due to the heat wave here probably), this is the first real update in quite some time. I asked you to send in some benchmark results and indeed I got a nice feedback. In this first part I will just quickly talk about what has been measured, and give the reported data the second part will interpret the data.
What the code measures
The code is doing the following. First it will do a little warm up, doing some allocations untimed. This gives the memory system a chance to prepare for what is coming :)
The program will then do a million operations of vm_allocate and vm_deallocate to factor out the overhead for allocation an deallocation, since the primary interest of this benchmark is the page faulting (with the zero filling). The reason 1 mio operations are done, is so that the runtime can be easily converted into us/operation. A runtime of 10s means 10us per iteration.
The first loop just does vm_allocate() and vm_deallocate(). The second does the same thing, except touches a single page within the allocation. This triggers a fault, a vm_object() allocation, and zero-fill. Then when we call vm_deallocate(), there is additional work to free the page and the object.
The third loop allocates and frees two pages, akin to the first loop. Finally, the fourth loop does the same for 2 pages per allocation, isolating out the per-page costs (fault, zero-fill, and free).
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The measured results
I had to name one entry Anonymous because it was submitted with 10.3 and AFAIK that's already problematic with Apple's touchy-feely lawyers...
| CPU/ Machine | OS | Submitter |
|---|
| 1p alloc | 1p alloc + fault | 2p alloc | 2p alloc + fault |
|---|
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1.25GHz G4 (167MHz system bus) | unknown
| Jim Magee |
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9.03s | 18.13s | N/A | 24.58s
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1 GHz G4 | 10.2.6 | F.Inci
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| 11.2s | 24.0s | 11.5s | 33.6s
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| 867 MHz G4 (Powerbook) | 10.2.6 | F. Inci
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16.5s | 34.5s | 17.0s | 47.7s
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500 MHz G4 | 10.3 | Anonymous
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14.9s | 39.4s | 14.9s | 50.5s
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| 800 MHz G4 (iMac) | 10.2.6 | H. Hess
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16.4s | 47.7s | 17.8s | 71.4s
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450 MHz G4 (Cube) | 10.2.6 | Nat!
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18.1s | 51.2s | 18.5s | 75.1s
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500 MHz G3 (IBook) | unknown | R.Lutz
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21.2s | 59.8s | 22.1s | 84.4s |
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