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view src/core/ngx_shmtx.h @ 6250:0256738454dc

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Increased the default number of output buffers. Since an output buffer can only be used for either reading or sending, small amounts of data left from the previous operation (due to some limits) must be sent before nginx will be able to read further into the buffer. Using only one output buffer can result in suboptimal behavior that manifests itself in forming and sending too small chunks of data. This is particularly painful with SPDY (or HTTP/2) where each such chunk needs to be prefixed with some header. The default flow-control window in HTTP/2 is 64k minus one bytes. With one 32k output buffer this results is one byte left after exhausting the window. With two 32k buffers the data will be read into the second free buffer before sending, thus the minimum output is increased to 32k + 1 bytes which is much better.
author Valentin Bartenev <vbart@nginx.com>
date Tue, 15 Sep 2015 17:49:15 +0300
parents 512c741fa841
children
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/*
 * Copyright (C) Igor Sysoev
 * Copyright (C) Nginx, Inc.
 */


#ifndef _NGX_SHMTX_H_INCLUDED_
#define _NGX_SHMTX_H_INCLUDED_


#include <ngx_config.h>
#include <ngx_core.h>


typedef struct {
    ngx_atomic_t   lock;
#if (NGX_HAVE_POSIX_SEM)
    ngx_atomic_t   wait;
#endif
} ngx_shmtx_sh_t;


typedef struct {
#if (NGX_HAVE_ATOMIC_OPS)
    ngx_atomic_t  *lock;
#if (NGX_HAVE_POSIX_SEM)
    ngx_atomic_t  *wait;
    ngx_uint_t     semaphore;
    sem_t          sem;
#endif
#else
    ngx_fd_t       fd;
    u_char        *name;
#endif
    ngx_uint_t     spin;
} ngx_shmtx_t;


ngx_int_t ngx_shmtx_create(ngx_shmtx_t *mtx, ngx_shmtx_sh_t *addr,
    u_char *name);
void ngx_shmtx_destroy(ngx_shmtx_t *mtx);
ngx_uint_t ngx_shmtx_trylock(ngx_shmtx_t *mtx);
void ngx_shmtx_lock(ngx_shmtx_t *mtx);
void ngx_shmtx_unlock(ngx_shmtx_t *mtx);
ngx_uint_t ngx_shmtx_force_unlock(ngx_shmtx_t *mtx, ngx_pid_t pid);


#endif /* _NGX_SHMTX_H_INCLUDED_ */