Linked by Thom Holwerda on Fri 2nd Sep 2005 09:44 UTC
Talk, Rumors, X Versus Y "We will shed more light on the whole Apple versus x86 PC, IBM G5 versus Intel CPU discussion by showing you what the G5 is capable of when running Linux. This gives us insight on the strength and weakness of Mac OS X, as we compare Linux and Mac OS X on the same machine."
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RE: Deceiving.
by japail on Fri 2nd Sep 2005 18:41 UTC in reply to "Deceiving."
japail
Member since:
2005-06-30

No, your understanding of the BSD subsystem in XNU is completely wrong. The BSD subsystem is responsible for managing processes, users, networking, the VFS, and numerous other things. This is largely why OS X has such coarse locking, despite using Mach 3.0 as the base. Much of the actual user-level operating system is provided by the BSD subsystem in terms of Mach primitives, and when XNU moved from FreeBSD/NetBSD/NeXT code it used they were all lacking fine-grained multithreading and Apple has had to gradually improve this. POSIX threads in XNU are implemented in terms of Mach threads (they're not green threads, which would probably improve their performance characteristics in certain ways and remove the seen scaling performance improvement at 2 cuncurrent connections among decreases elsewhere).

Reply Parent Score: 2

RE[2]: Deceiving.
by bryanv on Fri 2nd Sep 2005 18:51 in reply to "RE: Deceiving."
bryanv Member since:
2005-08-26

Thank God. I was hoping I was wrong. :-)

So what we're seeing is terrible thread creation times, scheduling problems, and perhaps even leftovers of the BGL?

Reply Parent Score: 1

RE[3]: Deceiving.
by japail on Fri 2nd Sep 2005 19:01 in reply to "RE[2]: Deceiving."
japail Member since:
2005-06-30

I think that it's likely a combination of the coarse locking (which Apple has been improving continually, but it's a long complicated process as Linux and the BSDs will attest to) and also Mach (which suffers from various performance problems remedied by modern microkernels like L4).

Reply Parent Score: 1