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view src/os/win32/ngx_atomic.h @ 7583:efd71d49bde0

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Events: available bytes calculation via ioctl(FIONREAD). This makes it possible to avoid looping for a long time while working with a fast enough peer when data are added to the socket buffer faster than we are able to read and process them (ticket #1431). This is basically what we already do on FreeBSD with kqueue, where information about the number of bytes in the socket buffer is returned by the kevent() call. With other event methods rev->available is now set to -1 when the socket is ready for reading. Later in ngx_recv() and ngx_recv_chain(), if full buffer is received, real number of bytes in the socket buffer is retrieved using ioctl(FIONREAD). Reading more than this number of bytes ensures that even with edge-triggered event methods the event will be triggered again, so it is safe to stop processing of the socket and switch to other connections. Using ioctl(FIONREAD) only after reading a full buffer is an optimization. With this approach we only call ioctl(FIONREAD) when there are at least two recv()/readv() calls.
author Maxim Dounin <mdounin@mdounin.ru>
date Thu, 17 Oct 2019 16:02:19 +0300
parents 2cd019520210
children
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/*
 * 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>


#define NGX_HAVE_ATOMIC_OPS   1

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 defined( __WATCOMC__ ) || defined( __BORLANDC__ ) || defined(__GNUC__)    \
    || ( _MSC_VER >= 1300 )

/* the new SDK headers */

#define ngx_atomic_cmp_set(lock, old, set)                                    \
    ((ngx_atomic_uint_t) InterlockedCompareExchange((long *) lock, set, old)  \
                         == old)

#else

/* the old MS VC6.0SP2 SDK headers */

#define ngx_atomic_cmp_set(lock, old, set)                                    \
    (InterlockedCompareExchange((void **) lock, (void *) set, (void *) old)   \
     == (void *) old)

#endif


#define ngx_atomic_fetch_add(p, add) InterlockedExchangeAdd((long *) p, add)


#define ngx_memory_barrier()


#if defined( __BORLANDC__ ) || ( __WATCOMC__ < 1230 )

/*
 * Borland C++ 5.5 (tasm32) and Open Watcom C prior to 1.3
 * do not understand the "pause" instruction
 */

#define ngx_cpu_pause()
#else
#define ngx_cpu_pause()       __asm { 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_ */