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runtime: fix darwin/amd64 thread VM footprint

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On darwin amd64 it was impossible to create more that ~132 threads. While
investigating I noticed that go consumes almost 1TB of virtual memory per
OS thread and the reason for such a small limit of OS thread was because
process was running out of virtual memory. While looking at bsdthread_create
I noticed that on amd64 it wasn't using PTHREAD_START_CUSTOM.
If you look at http://fxr.watson.org/fxr/source/bsd/kern/pthread_synch.c?v=xnu-1228
you will see that in that case darwin will use stack pointer as stack size,
allocating huge amounts of memory for stack. This change fixes the issue
and allows for creation of up to 2560 OS threads (which appears to be some
Mac OS X limit) with relatively small virtual memory consumption.

R=rsc
CC=golang-dev
https://golang.org/cl/4289075
This commit is contained in:
Alexey Borzenkov 2011-03-27 17:15:48 -04:00 committed by Russ Cox
parent ffb0a2d42a
commit 59a8926829
1 changed files with 1 additions and 2 deletions
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3
src/pkg/runtime/darwin/amd64/sys.s
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@ -146,8 +146,7 @@ TEXT runtime·bsdthread_create(SB),7,$0
MOVQ mm+16(SP), SI // "arg"
MOVQ stk+8(SP), DX // stack
MOVQ gg+24(SP), R10 // "pthread"
// TODO(rsc): why do we get away with 0 flags here but not on 386?
MOVQ $0, R8 // flags
MOVQ $0x01000000, R8 // flags = PTHREAD_START_CUSTOM
MOVQ $0, R9 // paranoia
MOVQ $(0x2000000+360), AX // bsdthread_create
SYSCALL