Mercurial > hg > nginx
view src/core/ngx_rwlock.c @ 7670:ccb5ff87ab3e
Cache: introduced min_free cache clearing.
Clearing cache based on free space left on a file system is
expected to allow better disk utilization in some cases, notably
when disk space might be also used for something other than nginx
cache (including nginx own temporary files) and while loading
cache (when cache size might be inaccurate for a while, effectively
disabling max_size cache clearing).
Based on a patch by Adam Bambuch.
author | Maxim Dounin <mdounin@mdounin.ru> |
---|---|
date | Mon, 22 Jun 2020 18:03:00 +0300 |
parents | d1816a2696de |
children | 7752d8523066 |
line wrap: on
line source
/* * Copyright (C) Ruslan Ermilov * Copyright (C) Nginx, Inc. */ #include <ngx_config.h> #include <ngx_core.h> #if (NGX_HAVE_ATOMIC_OPS) #define NGX_RWLOCK_SPIN 2048 #define NGX_RWLOCK_WLOCK ((ngx_atomic_uint_t) -1) void ngx_rwlock_wlock(ngx_atomic_t *lock) { ngx_uint_t i, n; for ( ;; ) { if (*lock == 0 && ngx_atomic_cmp_set(lock, 0, NGX_RWLOCK_WLOCK)) { return; } if (ngx_ncpu > 1) { for (n = 1; n < NGX_RWLOCK_SPIN; n <<= 1) { for (i = 0; i < n; i++) { ngx_cpu_pause(); } if (*lock == 0 && ngx_atomic_cmp_set(lock, 0, NGX_RWLOCK_WLOCK)) { return; } } } ngx_sched_yield(); } } void ngx_rwlock_rlock(ngx_atomic_t *lock) { ngx_uint_t i, n; ngx_atomic_uint_t readers; for ( ;; ) { readers = *lock; if (readers != NGX_RWLOCK_WLOCK && ngx_atomic_cmp_set(lock, readers, readers + 1)) { return; } if (ngx_ncpu > 1) { for (n = 1; n < NGX_RWLOCK_SPIN; n <<= 1) { for (i = 0; i < n; i++) { ngx_cpu_pause(); } readers = *lock; if (readers != NGX_RWLOCK_WLOCK && ngx_atomic_cmp_set(lock, readers, readers + 1)) { return; } } } ngx_sched_yield(); } } void ngx_rwlock_unlock(ngx_atomic_t *lock) { ngx_atomic_uint_t readers; readers = *lock; if (readers == NGX_RWLOCK_WLOCK) { (void) ngx_atomic_cmp_set(lock, NGX_RWLOCK_WLOCK, 0); return; } for ( ;; ) { if (ngx_atomic_cmp_set(lock, readers, readers - 1)) { return; } readers = *lock; } } void ngx_rwlock_downgrade(ngx_atomic_t *lock) { if (*lock == NGX_RWLOCK_WLOCK) { *lock = 1; } } #else #if (NGX_HTTP_UPSTREAM_ZONE || NGX_STREAM_UPSTREAM_ZONE) #error ngx_atomic_cmp_set() is not defined! #endif #endif