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io: use posix_fadvise() instead of readahead() #404

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Merged
merged 1 commit into from
Nov 6, 2018
Merged

io: use posix_fadvise() instead of readahead() #404

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1 change: 1 addition & 0 deletions CMakeLists.txt
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Original file line number Diff line number Diff line change
Expand Up @@ -200,6 +200,7 @@ check_function_exists(mach_absolute_time HAVE_MACH_ABSOLUTE_TIME)
check_function_exists(mach_approximate_time HAVE_MACH_APPROXIMATE_TIME)
check_function_exists(mach_port_construct HAVE_MACH_PORT_CONSTRUCT)
check_function_exists(malloc_create_zone HAVE_MALLOC_CREATE_ZONE)
check_function_exists(posix_fadvise HAVE_POSIX_FADVISE)
check_function_exists(pthread_key_init_np HAVE_PTHREAD_KEY_INIT_NP)
check_function_exists(pthread_main_np HAVE_PTHREAD_MAIN_NP)
check_function_exists(pthread_workqueue_setdispatch_np HAVE_PTHREAD_WORKQUEUE_SETDISPATCH_NP)
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3 changes: 3 additions & 0 deletions cmake/config.h.in
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Expand Up @@ -132,6 +132,9 @@
/* Define if you have the Objective-C runtime */
#cmakedefine HAVE_OBJC

/* Define to 1 if you have the `posix_fadvise' function. */
#cmakedefine HAVE_POSIX_FADVISE

/* Define to 1 if you have the `pthread_key_init_np' function. */
#cmakedefine HAVE_PTHREAD_KEY_INIT_NP

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29 changes: 14 additions & 15 deletions src/io.c
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Expand Up @@ -20,11 +20,6 @@

#include "internal.h"

#if defined(__FreeBSD__)
#include <fcntl.h>
#define F_RDADVISE F_RDAHEAD
#endif

#ifndef DISPATCH_IO_DEBUG
#define DISPATCH_IO_DEBUG DISPATCH_DEBUG
#endif
Expand Down Expand Up @@ -2235,9 +2230,8 @@ _dispatch_operation_advise(dispatch_operation_t op, size_t chunk_size)
(void)chunk_size;
#else
if (_dispatch_io_get_error(op, NULL, true)) return;
#if defined(__linux__) || defined(__FreeBSD__)
// linux does not support fcntl (F_RDAVISE)
// define necessary datastructure and use readahead
#if !defined(F_RDADVISE)
// Compatibility struct whose values may be passed to posix_fadvise()
struct radvisory {
off_t ra_offset;
int ra_count;
Expand All @@ -2262,20 +2256,25 @@ _dispatch_operation_advise(dispatch_operation_t op, size_t chunk_size)
}
advise.ra_offset = op->advise_offset;
op->advise_offset += advise.ra_count;
#if defined(__linux__)
_dispatch_io_syscall_switch(err,
readahead(op->fd_entry->fd, advise.ra_offset, (size_t)advise.ra_count),
case EINVAL: break; // fd does refer to a non-supported filetype
default: (void)dispatch_assume_zero(err); break;
);
#else
#if defined(F_RDADVISE)
_dispatch_io_syscall_switch(err,
fcntl(op->fd_entry->fd, F_RDADVISE, &advise),
case EFBIG: break; // advised past the end of the file rdar://10415691
case ENOTSUP: break; // not all FS support radvise rdar://13484629
// TODO: set disk status on error
default: (void)dispatch_assume_zero(err); break;
);
#elif defined(HAVE_POSIX_FADVISE)
err = posix_fadvise(op->fd_entry->fd, advise.ra_offset,
(off_t)advise.ra_count, POSIX_FADV_WILLNEED);
switch (err) {
case 0: break;
case EINVAL: break; // unsupported advice or file type
case ESPIPE: break; // fd refers to a pipe or FIFO
default: (void)dispatch_assume_zero(err); break;
}
#else
#error "_dispatch_operation_advise not implemented on this platform"
#endif
#endif
}
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