06-03-2002
Writing fast and efficiently - how ?
I have a lot of processes all of which need to write quite
a lot of data to the filesystem ( to a single file).
This is managed today in the following way : all the processes
write the data to a shared memory block, which is manged by a process that empties it to a file, thus allowing more space for
writing by the other processes.
It is now argued that this is slow and time- consuming,
specifically in times of high load on the shmem resource
(since each read/write is performed via a lock management
facility).
My question is : Will it be faster to dump the whole idea
of the shared memory and use the buffers that the O.S
provudes ? What type of locking will then be necessary ?
I am working on a AIX , RS6000 machine.
Thank you in advance for your comments !
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LEARN ABOUT OPENSOLARIS
pthread_rwlockattr_getpshared
pthread_rwlockattr_getpshared(3C) Standard C Library Functions pthread_rwlockattr_getpshared(3C)
NAME
pthread_rwlockattr_getpshared, pthread_rwlockattr_setpshared - get or set process-shared attribute of read-write lock attributes object
SYNOPSIS
cc -mt [ flag... ] file... -lpthread [ library... ]
#include <pthread.h>
int pthread_rwlockattr_getpshared(
const pthread_rwlockattr_t *restrict attr,
int *restrict pshared);
int pthread_rwlockattr_setpshared(pthread_rwlockattr_t *attr,
int pshared);
DESCRIPTION
The process-shared attribute is set to PTHREAD_PROCESS_SHARED to permit a read-write lock to be operated upon by any thread that has
access to the memory where the read-write lock is allocated, even if the read-write lock is allocated in memory that is shared by multiple
processes. If the process-shared attribute is PTHREAD_PROCESS_PRIVATE, the read-write lock will only be operated upon by threads created
within the same process as the thread that initialised the read-write lock; if threads of differing processes attempt to operate on such a
read-write lock, the behaviour is undefined. The default value of the process-shared attribute is PTHREAD_PROCESS_PRIVATE.
The pthread_rwlockattr_getpshared() function obtains the value of the process-shared attribute from the initialised attributes object ref-
erenced by attr. The pthread_rwlockattr_setpshared() function is used to set the process-shared attribute in an initialised attributes
object referenced by attr.
RETURN VALUES
If successful, the pthread_rwlockattr_setpshared() function returns 0. Otherwise, an error number is returned to indicate the error.
Upon successful completion, the pthread_rwlockattr_getpshared() returns 0 and stores the value of the process-shared attribute of attr
into the object referenced by the pshared parameter. Otherwise an error number is returned to indicate the error.
ERRORS
The pthread_rwlockattr_getpshared() and pthread_rwlockattr_setpshared() functions will fail if:
EINVAL The value specified by attr or pshared is invalid.
ATTRIBUTES
See attributes(5) for descriptions of the following attributes:
+-----------------------------+-----------------------------+
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+-----------------------------+-----------------------------+
|Interface Stability |Standard |
+-----------------------------+-----------------------------+
|MT-Level |MT-Safe |
+-----------------------------+-----------------------------+
SEE ALSO
pthread_rwlock_init(3C), pthread_rwlock_rdlock(3C), pthread_rwlock_unlock(3C), pthread_rwlock_wrlock(3C), pthread_rwlockattr_init(3C),
attributes(5), standards(5)
SunOS 5.11 23 Mar 2005 pthread_rwlockattr_getpshared(3C)