Re: cross-bounday memory communication b/w user app and the Kernel.How?
Re: cross-bounday memory communication b/w user app and the Kernel.How?
- Subject: Re: cross-bounday memory communication b/w user app and the Kernel.How?
- From: Michael Smith <email@hidden>
- Date: Mon, 5 Jun 2006 09:40:46 -0700
On Jun 5, 2006, at 7:52 AM, Andrew Gallatin wrote:
I'm simply trying to account for why it takes ~8x as long for a simple
syscall,
Which "simple" syscall?
and ~4x as long to get an ioctl into our driver when running
MacOSX vs ppc64 linux on the same hardware. On x86 linux, when
switching from the 1G/3G split to 4G/4G, we see a similar bloat of
ioctl times. I had simply assumed that the 4G address space was the
issue. Perhaps more of the blame lies elsewhere.
Syscall entry/exit is certainly more expensive on Mac OS than Linux.
It comprises such a miniscule part of the elapsed system time on
typical systems that whilst it shows up a lot on micro-benchmarks,
it's not a very rewarding target for optimisation.
= Mike
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