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| | Memory segment - Wikipedia, the free encyclopedia |
 | | On the Intel x86 architecture, a memory segment is the portion of memory which may be addressed by a single index register without changing a 16-bit segment selector. | | | Segmentation is a virtual memory scheme, like paging which although is supported on x86, is not supported on many other architectures. | | | In 16-bit real mode, enabling applications to make use of multiple memory segments (in order to access more memory than available in any one 64K-segment) was quite complex, but was viewed as a necessary evil for all but the smallest tools (which could do with less memory). |
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http://en.wikipedia.org/wiki/Memory_segment
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| | Segment - Wikipedia, the free encyclopedia |
| | Memory segment, the portion of computer memory which may be addressed by a single index register. | | | Network segment, a part of a larger computer network. | | | A Protocol data unit of the transport layer in computing. |
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http://en.wikipedia.org/wiki/Segment
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| | CS 537 - Memory Management |
| | The selector is used to fetch a segment descriptor from a table (actually, there are two tables and one of the bits of the selector is used to choose which table). | | | This is the way segmentation works in Multics, the granddaddy of all modern operating systems and a pioneer of the idea of segmentation. | | | Segmentation caries this feature one step further by allowing each process to have multiple ``simulated memories.'' Each of these memories (called a segment) starts at address zero, is independently protected, and can be separately paged. |
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http://www.cs.wisc.edu/~solomon/cs537/segmentation.html
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| | Explore the Linux memory model |
| | Kernel comparison: Improved memory management in the 2.6 kernel (developerWorks, March 2004) details new techniques to improve the use of large amounts of memory, reverse mapping, storage of page-table entries in high memory, and the greater stability of the memory manager. | | | The segment descriptor entry contains both a pointer to the first byte in the associated segment represented by the Base field and a 20-bit value (the Limit field) which represents the size of the segment in memory. | | | Inside memory management (developerWorks, November 2004) provides an overview of the memory management techniques that are available in Linux, including how memory management works, how to manage memory manually, semi-manually, and automatically. |
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http://www-128.ibm.com/developerworks/linux/library/l-memmod/?ca=dgr-lnxw01MemModel
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| | IPC:Shared Memory |
| | Whether to share memory or to share data contained in the file, when multiple process map a file simultaneously there may be problems with simultaneous access to data elements. | | | In a system with fixed memory (non-virtual), the address space of a process occupies and is limited to a portion of the system's main memory. | | | Solaris 2.x also supports System V shared memory, which is another way to let multiple processes attach a segment of physical memory to their virtual address spaces. |
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http://www.cs.cf.ac.uk/Dave/C/node27.html
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| | Atrevida Tutorial 4: Memory in the PC |
| | Segments can start in memory every sixteen bytes, so the first segment (segment 0) starts at physical address 0, the second segment (segment 1) starts at physical address 16 dec (10 hex), the third segment (segment 2) starts at physical address 32 dec (20 hex), and so on. | | | Segment A000 hex is set aside for use with graphics modes of the computer's video card. | | | To access all of these bytes, we could assign each memory location an address: the first byte would have the address 0, the second would have the address 1, the third would have address 2, and so on, and the last byte would have the address 1048575 dec (because we started at zero, not one). |
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http://atrevida.comprenica.com/atrtut04.html
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| | Protected-Mode Memory Management |
| | After loading a page from disk and remapping it to physical memory, the operating system reexecutes the instruction which caused the page fault exception to occur, so the running application is not even aware of the fact that part of its memory was stored temporarily on disk. | | | Decreasing the segment limit value in an expand-down segment causes memory to be allocated at the bottom of the segment. | | | Descriptor tables reside in system memory and are used by the processor to perform address translation. |
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http://www.internals.com/articles/protmode/protmode.htm
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| | The DB2 UDB memory model |
| | Segment B (purple) is allocated to application group shared memory, because the database is intra_parallel enabled. | | | Memory Windows enable quadrant 3 to be a private shared memory space for a process group as defined in /etc/services.window. | | | This memory is used by database level tasks such as backup/restore, locking, and SQL executions. |
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http://www-106.ibm.com/developerworks/db2/library/techarticle/dm-0406qi
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| | NSPR Reference: Chapter 28 Named Shared Memory |
| | The Unix implementation may use SysV IPC shared memory, Posix shared memory, or memory mapped files; the filename may be used to define the namespace. | | | The NSPR shared memory API provides a cross-platform named shared-memory interface that is modeled on similar constructs in the Unix and Windows operating systems. | | | The address to which the shared memory segment is mapped. |
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http://www.mozilla.org/projects/nspr/reference/html/prshm.html
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| | Shared Memory Segments |
| | Semaphores to lock the shared memory segment while a process is writing to it. | | | The cool thing about shared memory segments is that they are what they sound like: a segment of memory that is shared between processes. | | | Well, since you have multiple processes modifying the shared memory segment, it is possible that certain errors could crop up when updates to the segment occur simultaneously. |
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http://www.ecst.csuchico.edu/~beej/guide/ipc/shmem.html
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| | Apache Portable Runtime: Shared Memory Routines |
| | Attach to a shared memory segment that was created by another process. | | | Retrieve the length of a shared memory segment in bytes. | | | The shared memory segment from which to retrieve the base address. |
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http://apr.apache.org/docs/apr/group__apr__shm.html
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| | Manual page for shmop(2) |
| | The available data space is not large enough to accommodate the shared memory segment. | | | The user must explicitly remove shared memory segments after the last reference to them has been removed. | | | shmdt() fails and does not detach the shared memory segment if shmaddr is not the data segment start address of a shared memory segment. |
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http://www.cs.utk.edu/~cs460.is&r/cgi-bin/group4/collection/shmdt.2.html
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| | Exercises 3: Packet Segmentation Overhead (U.Crete, CS-534) |
| | For reasons of simplicity of memory management, again, each such IP packet is written into two different memory segments --hence, approximately 128-68 = 60 bytes remain unused in every other segment (30 bytes per segment average fragmentation overhead). | | | This is a "bad" size for our buffer memory, because it is just above our segment size (we assume that IP packet sizes are multiples of 4 bytes, otherwise, 65 bytes would be the worst size in this case). | | | This is the size of the smallest packet as stored in memory; For example, for IP, this is taken to be 40 bytes. |
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http://www.ics.forth.gr/~kateveni/534/05a/ex03_segmnt.html
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| | D/121B Board & E000 Memory Segment Considerations |
| | If the D/121B bus mode does not match the computer's default E000 memory segment operation, the board firmware will not download and you will receive an error message indicating that there was an error configuring the board at the base offset address. | | | Note that this guideline is a general case, and may not be true for every computer. | | | If your computer defaults to 8-bit operation, and your D/121B is operating in 8-bit bus mode, a problem may occur if a 16-bit board from another manufacturer is installed in free space in the E000 segment. |
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http://resource.intel.com/telecom/support/Tnotes/mult_pg/tn001.htm
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| | A1 (code) |
| | It requires gcc 2.4.2 or higher and is portable to computers with memory segment protection. | | | This article was originally based on material from the Free On-line Dictionary of Computing, which is [Foldoc licenselicensed] under the GFDL. |
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http://encycl.opentopia.com/term/A1_(code)
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| | CPU Instruction Set As an Artistic Object and the History of Classic CPU Instruction Sets |
| | Most memory mapped file interfaces have the concept of a window on the file that is mapped into the process's address space - PAE can reduce the cost of a window remapping from that of a disk transfer (milliseconds) to that of a simple system call (microseconds). | | | Memory is much slower then CPU registers, so it is a bottleneck that designers try to resolve implementing multilevel caching L1/L2/L3trying to capitalize of the locality of references in most programs. | | | Shared memory vector multiprocessors became the formula for scientific computing that is likely to continue well into the 21st century. |
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http://www.softpanorama.org/History/cpu_history.shtml
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| | Asking for a Shared Memory Segment - shmget() |
| | Similarly, if process 2 requests the same shared memory segment with the same key value, process 2 will be granted the right to use the shared memory segment; but it is not yet part of the address space of process 2. | | | It is the numeric key to be assigned to the returned shared memory segment. | | | The purpose of flag is to specify the way that the shared memory will be used. |
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http://www.csl.mtu.edu/cs4411.ck/www/NOTES/process/shm/shmget.html
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| | PHP: Shared Memory Functions - Manual |
| | So basically, the purpose of shmop is to provide a symple interface to shared memory that can be used with OTHER NON php shm creators. | | | So correct me if I'm wrong, but the shmop.c extension uses memcpy() to copy strings to and from shared memory without any form of locking, and as far as I know, memcpy() is not atomic. | | | It's not the job of the shmop extension to provide locking, there are many locking schemes avalible, if you need some sort of atomic operations choose a locking scheme that suits you and use it. |
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http://us2.php.net/manual/en/ref.shmop.php
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| | [No title] |
| | The user must ensure that a segment is eventually destroyed; otherwise its pages that were faulted in will remain in memory or swap. | | | In the future, these man be modified as needed or moved to a proc file system interface. | | | SHM_UNLOCK allows the shared memory segment to be swapped out. |
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http://www.ibiblio.org/gferg/ldp/man/man2/shmctl.2.html
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| | Virtual memory segment in Informix |
| | The larger the virtual memory segment, the better the performance because the database can read data from cache instead of disk. | | | You can also use glance to determine the free memory on your system, to help size the onconfig file appropriately. | | | If your Informix database is being used with some third party software, check with the application vendor and see if they have any recommendations. |
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http://expertanswercenter.techtarget.com/eac/knowledgebaseAnswer/0,295199,sid63_gci979074,00.html
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