Mercurial > hg > nginx-quic
view src/os/unix/ngx_atomic.h @ 4667:d05ab8793a69 stable-1.2
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.
author | Maxim Dounin <mdounin@mdounin.ru> |
---|---|
date | Mon, 04 Jun 2012 11:21:58 +0000 |
parents | d620f497c50f |
children | 4c36e15651f7 |
line wrap: on
line source
/* * Copyright (C) Igor Sysoev * Copyright (C) Nginx, Inc. */ #ifndef _NGX_ATOMIC_H_INCLUDED_ #define _NGX_ATOMIC_H_INCLUDED_ #include <ngx_config.h> #include <ngx_core.h> #if (NGX_HAVE_LIBATOMIC) #define AO_REQUIRE_CAS #include <atomic_ops.h> #define NGX_HAVE_ATOMIC_OPS 1 typedef long ngx_atomic_int_t; typedef AO_t ngx_atomic_uint_t; typedef volatile ngx_atomic_uint_t ngx_atomic_t; #if (NGX_PTR_SIZE == 8) #define NGX_ATOMIC_T_LEN (sizeof("-9223372036854775808") - 1) #else #define NGX_ATOMIC_T_LEN (sizeof("-2147483648") - 1) #endif #define ngx_atomic_cmp_set(lock, old, new) \ AO_compare_and_swap(lock, old, new) #define ngx_atomic_fetch_add(value, add) \ AO_fetch_and_add(value, add) #define ngx_memory_barrier() AO_nop() #define ngx_cpu_pause() #elif (NGX_DARWIN_ATOMIC) /* * use Darwin 8 atomic(3) and barrier(3) operations * optimized at run-time for UP and SMP */ #include <libkern/OSAtomic.h> /* "bool" conflicts with perl's CORE/handy.h */ #undef bool #define NGX_HAVE_ATOMIC_OPS 1 #if (NGX_PTR_SIZE == 8) typedef int64_t ngx_atomic_int_t; typedef uint64_t ngx_atomic_uint_t; #define NGX_ATOMIC_T_LEN (sizeof("-9223372036854775808") - 1) #define ngx_atomic_cmp_set(lock, old, new) \ OSAtomicCompareAndSwap64Barrier(old, new, (int64_t *) lock) #define ngx_atomic_fetch_add(value, add) \ (OSAtomicAdd64(add, (int64_t *) value) - add) #else typedef int32_t ngx_atomic_int_t; typedef uint32_t ngx_atomic_uint_t; #define NGX_ATOMIC_T_LEN (sizeof("-2147483648") - 1) #define ngx_atomic_cmp_set(lock, old, new) \ OSAtomicCompareAndSwap32Barrier(old, new, (int32_t *) lock) #define ngx_atomic_fetch_add(value, add) \ (OSAtomicAdd32(add, (int32_t *) value) - add) #endif #define ngx_memory_barrier() OSMemoryBarrier() #define ngx_cpu_pause() typedef volatile ngx_atomic_uint_t ngx_atomic_t; #elif (NGX_HAVE_GCC_ATOMIC) /* GCC 4.1 builtin atomic operations */ #define NGX_HAVE_ATOMIC_OPS 1 typedef long ngx_atomic_int_t; typedef unsigned long ngx_atomic_uint_t; #if (NGX_PTR_SIZE == 8) #define NGX_ATOMIC_T_LEN (sizeof("-9223372036854775808") - 1) #else #define NGX_ATOMIC_T_LEN (sizeof("-2147483648") - 1) #endif typedef volatile ngx_atomic_uint_t ngx_atomic_t; #define ngx_atomic_cmp_set(lock, old, set) \ __sync_bool_compare_and_swap(lock, old, set) #define ngx_atomic_fetch_add(value, add) \ __sync_fetch_and_add(value, add) #define ngx_memory_barrier() __sync_synchronize() #if ( __i386__ || __i386 || __amd64__ || __amd64 ) #define ngx_cpu_pause() __asm__ ("pause") #else #define ngx_cpu_pause() #endif #elif ( __i386__ || __i386 ) typedef int32_t ngx_atomic_int_t; typedef uint32_t ngx_atomic_uint_t; typedef volatile ngx_atomic_uint_t ngx_atomic_t; #define NGX_ATOMIC_T_LEN (sizeof("-2147483648") - 1) #if ( __SUNPRO_C ) #define NGX_HAVE_ATOMIC_OPS 1 ngx_atomic_uint_t ngx_atomic_cmp_set(ngx_atomic_t *lock, ngx_atomic_uint_t old, ngx_atomic_uint_t set); ngx_atomic_int_t ngx_atomic_fetch_add(ngx_atomic_t *value, ngx_atomic_int_t add); /* * Sun Studio 12 exits with segmentation fault on '__asm ("pause")', * so ngx_cpu_pause is declared in src/os/unix/ngx_sunpro_x86.il */ void ngx_cpu_pause(void); /* the code in src/os/unix/ngx_sunpro_x86.il */ #define ngx_memory_barrier() __asm (".volatile"); __asm (".nonvolatile") #else /* ( __GNUC__ || __INTEL_COMPILER ) */ #define NGX_HAVE_ATOMIC_OPS 1 #include "ngx_gcc_atomic_x86.h" #endif #elif ( __amd64__ || __amd64 ) typedef int64_t ngx_atomic_int_t; typedef uint64_t ngx_atomic_uint_t; typedef volatile ngx_atomic_uint_t ngx_atomic_t; #define NGX_ATOMIC_T_LEN (sizeof("-9223372036854775808") - 1) #if ( __SUNPRO_C ) #define NGX_HAVE_ATOMIC_OPS 1 ngx_atomic_uint_t ngx_atomic_cmp_set(ngx_atomic_t *lock, ngx_atomic_uint_t old, ngx_atomic_uint_t set); ngx_atomic_int_t ngx_atomic_fetch_add(ngx_atomic_t *value, ngx_atomic_int_t add); /* * Sun Studio 12 exits with segmentation fault on '__asm ("pause")', * so ngx_cpu_pause is declared in src/os/unix/ngx_sunpro_amd64.il */ void ngx_cpu_pause(void); /* the code in src/os/unix/ngx_sunpro_amd64.il */ #define ngx_memory_barrier() __asm (".volatile"); __asm (".nonvolatile") #else /* ( __GNUC__ || __INTEL_COMPILER ) */ #define NGX_HAVE_ATOMIC_OPS 1 #include "ngx_gcc_atomic_amd64.h" #endif #elif ( __sparc__ || __sparc || __sparcv9 ) #if (NGX_PTR_SIZE == 8) typedef int64_t ngx_atomic_int_t; typedef uint64_t ngx_atomic_uint_t; #define NGX_ATOMIC_T_LEN (sizeof("-9223372036854775808") - 1) #else typedef int32_t ngx_atomic_int_t; typedef uint32_t ngx_atomic_uint_t; #define NGX_ATOMIC_T_LEN (sizeof("-2147483648") - 1) #endif typedef volatile ngx_atomic_uint_t ngx_atomic_t; #if ( __SUNPRO_C ) #define NGX_HAVE_ATOMIC_OPS 1 #include "ngx_sunpro_atomic_sparc64.h" #else /* ( __GNUC__ || __INTEL_COMPILER ) */ #define NGX_HAVE_ATOMIC_OPS 1 #include "ngx_gcc_atomic_sparc64.h" #endif #elif ( __powerpc__ || __POWERPC__ ) #define NGX_HAVE_ATOMIC_OPS 1 #if (NGX_PTR_SIZE == 8) typedef int64_t ngx_atomic_int_t; typedef uint64_t ngx_atomic_uint_t; #define NGX_ATOMIC_T_LEN (sizeof("-9223372036854775808") - 1) #else typedef int32_t ngx_atomic_int_t; typedef uint32_t ngx_atomic_uint_t; #define NGX_ATOMIC_T_LEN (sizeof("-2147483648") - 1) #endif typedef volatile ngx_atomic_uint_t ngx_atomic_t; #include "ngx_gcc_atomic_ppc.h" #endif #if !(NGX_HAVE_ATOMIC_OPS) #define NGX_HAVE_ATOMIC_OPS 0 typedef int32_t ngx_atomic_int_t; typedef uint32_t ngx_atomic_uint_t; typedef volatile ngx_atomic_uint_t ngx_atomic_t; #define NGX_ATOMIC_T_LEN (sizeof("-2147483648") - 1) static ngx_inline ngx_atomic_uint_t ngx_atomic_cmp_set(ngx_atomic_t *lock, ngx_atomic_uint_t old, ngx_atomic_uint_t set) { if (*lock == old) { *lock = set; return 1; } return 0; } static ngx_inline ngx_atomic_int_t ngx_atomic_fetch_add(ngx_atomic_t *value, ngx_atomic_int_t add) { ngx_atomic_int_t old; old = *value; *value += add; return old; } #define ngx_memory_barrier() #define ngx_cpu_pause() #endif void ngx_spinlock(ngx_atomic_t *lock, ngx_atomic_int_t value, ngx_uint_t spin); #define ngx_trylock(lock) (*(lock) == 0 && ngx_atomic_cmp_set(lock, 0, 1)) #define ngx_unlock(lock) *(lock) = 0 #endif /* _NGX_ATOMIC_H_INCLUDED_ */