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Writing fast and efficiently - how ?

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# 8  
Old 06-10-2002
I would look to the existing problem in a different way. The problem as stated intially is "formulating a faster technique for transfer of data from Shared Memory to a file" .
I would suggest to divide the shared memory into small segments and allow a pair of thread to read/write from each domain, in sync. Hence multiple threads operates on the data together but at mapped memory address. Each thread pointers should be intialized once to the domain bounday (addresses space). Once done a write thread of each process can write to a specific region incrementing a global resource each for itself. Meanwhile a read thread for each data division conditionally waits for the global variable to reach its max or upper domain limit. Once the event is initiated the write thread should conditionally wait for the variable to be initialized to the lower boud limit meanwhile the read thread should write the data to the file. Hence block I/O would be possible , which I think could be faster than the existing.
But however I do take an assumption that the order in which data has to writen to the file is immaterial.

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mman.h(3HEAD)                                                         Headers                                                        mman.h(3HEAD)

mman.h, mman - memory management declarations SYNOPSIS
#include <sys/mman.h> DESCRIPTION
The <sys/mman.h> header supports the following options: o the Memory Mapped Files option o the Shared Memory Objects option o the Process Memory Locking option o the Memory Protection option o the Synchronized Input and Output option For Memory Mapped Files and Shared Memory Objects options, the following protection options are defined: PROT_READ Page can be read. PROT_WRITE Page can be written. PROT_EXEC Page can be executed. PROT_NONE Page cannot be accessed. The following flag options are defined: MAP_SHARED Share changes. MAP_PRIVATE Changes are private. MAP_FIXED Interpret addr exactly. The flags immediately following are defined for msync(). See msync(3C). MS_ASYNC Perform asynchronous writes. MS_SYNC Perform synchronous writes. MS_INVALIDATE Invalidate mappings. The symbolic constants immediately following are defined for the mlockall() function. See mlockall(3C). MCL_CURRENT Lock currently mapped pages. MCL_FUTURE Lock pages that become mapped. The symbolic constant MAP_FAILED is defined to indicate a failure from the mmap() function. See mmap(2). The mode_t, off_t, and size_t types are be defined as described in <sys/types.h>. See types(3HEAD). ATTRIBUTES
See attributes(5) for descriptions of the following attributes: +-----------------------------+-----------------------------+ | ATTRIBUTE TYPE | ATTRIBUTE VALUE | +-----------------------------+-----------------------------+ |Interface Stability |Standard | +-----------------------------+-----------------------------+ SEE ALSO
mmap(2), mprotect(2), munmap(2), madvise(3C), mlock(3C), mlockall(3C), msync(3C), shm_open(3RT), shm_unlink(3RT), attributes(5), stan- dards(5) SunOS 5.10 10 Sep 2004 mman.h(3HEAD)

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