Merge of r4622, r4623: balancing changes. *) Upstream: smooth weighted round-robin balancing. For edge case weights like { 5, 1, 1 } we now produce { a, a, b, a, c, a, a } sequence instead of { c, b, a, a, a, a, a } produced previously. Algorithm is as follows: on each peer selection we increase current_weight of each eligible peer by its weight, select peer with greatest current_weight and reduce its current_weight by total number of weight points distributed among peers. In case of { 5, 1, 1 } weights this gives the following sequence of current_weight's: a b c 0 0 0 (initial state) 5 1 1 (a selected) -2 1 1 3 2 2 (a selected) -4 2 2 1 3 3 (b selected) 1 -4 3 6 -3 4 (a selected) -1 -3 4 4 -2 5 (c selected) 4 -2 -2 9 -1 -1 (a selected) 2 -1 -1 7 0 0 (a selected) 0 0 0 To preserve weight reduction in case of failures the effective_weight variable was introduced, which usually matches peer's weight, but is reduced temporarily on peer failures. This change also fixes loop with backup servers and proxy_next_upstream http_404 (ticket #47), and skipping alive upstreams in some cases if there are multiple dead ones (ticket #64). *) Upstream: fixed ip_hash rebalancing with the "down" flag. Due to weight being set to 0 for down peers, order of peers after sorting wasn't the same as without the "down" flag (with down peers at the end), resulting in client rebalancing for clients on other servers. The only rebalancing which should happen after adding "down" to a server is one for clients on the server. The problem was introduced in r1377 (which fixed endless loop by setting weight to 0 for down servers). The loop is no longer possible with new smooth algorithm, so preserving original weight is safe.

/*
 * Copyright (C) Igor Sysoev
 * Copyright (C) Nginx, Inc.
 */


#include <sys/syscall.h>
#include <machine/asm.h>

/*
 * rfork_thread(3) - rfork_thread(flags, stack, func, arg);
 */

#define	KERNCALL	int $0x80

ENTRY(rfork_thread)
	push	%ebp
	mov	%esp, %ebp
	push	%esi

	mov	12(%ebp), %esi	# the thread stack address

	sub	$4, %esi
	mov	20(%ebp), %eax	# the thread argument
	mov	%eax, (%esi)

	sub	$4, %esi
	mov	16(%ebp), %eax	# the thread start address
	mov	%eax, (%esi)

	push	8(%ebp)		# rfork(2) flags
	push	$0
	mov	$SYS_rfork, %eax
	KERNCALL
	jc	error

	cmp	$0, %edx
	jne	child

parent:
	add	$8, %esp
	pop	%esi
	leave
	ret

child:
	mov	%esi, %esp
	pop	%eax
	call	*%eax		# call a thread start address ...
	add	$4, %esp

	push	%eax
	push	$0
	mov	$SYS_exit, %eax	# ... and exit(2) after a thread would return
	KERNCALL

error:
	add	$8, %esp
	pop	%esi
	leave
	PIC_PROLOGUE

	/* libc's cerror: jmp  PIC_PLT(HIDENAME(cerror)) */

	push	%eax
	call	PIC_PLT(CNAME(__error))
	pop	%ecx
	PIC_EPILOGUE
	mov	%ecx, (%eax)
	mov	$-1, %eax
	mov	$-1, %edx
	ret