Changes between Version 39 and Version 40 of replication_distribution


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Timestamp:
Jun 26, 2018, 4:08:38 PM (3 years ago)
Author:
nicolas.van.phan@…
Comment:

Add links to referenced files and structures

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  • replication_distribution

    v39 v40  
    77 * The private segment containing the stack for a given thread is placed in the same cluster as the thread using it.
    88 * The shared segment containing the global data is distributed on all clusters as regularly as possible to avoid contention.
    9  * The segments dynamically allocated by the mmap() system call are placed  as described below.
     9 * The segments dynamically allocated by the [https://www-soc.lip6.fr/trac/almos-mkh/browser/trunk/kernel/syscalls/sys_mmap.c#L38 mmap()] system call are placed  as described below.
    1010
    1111To actually control data placement on the physical memory banks, the kernel uses the paged virtual memory MMU to map a virtual segment to a given physical memory bank.
    1212
    13 This replication / distribution policy is implemented by the Virtual Memory Manager (in the vmm.h / vmm.c files).
     13This replication / distribution policy is implemented by the Virtual Memory Manager (in the [https://www-soc.lip6.fr/trac/almos-mkh/browser/trunk/kernel/mm/vmm.h vmm.h] and [https://www-soc.lip6.fr/trac/almos-mkh/browser/trunk/kernel/mm/vmm.c vmm.c] files).
    1414
    1515A '''vseg''' is a contiguous memory zone in the process virtual space, where all adresses in this '''vseg''' can be accessed by the process without segmentation violation: if the corresponding is not mapped, the page fault will be handled by the kernel,
    16 and a physical page will be dynamically allocated and initialized if required. A '''vseg''' always contains  an integer number of pages. Depending on its type, a '''vseg''' has some specific attributes regarding access rights, replication policy, and distribution policy. The vseg descriptor is defined by the structure vseg_t in the ''vseg.h'' file.
     16and a physical page will be dynamically allocated and initialized if required. A '''vseg''' always contains  an integer number of pages. Depending on its type, a '''vseg''' has some specific attributes regarding access rights, replication policy, and distribution policy. The vseg descriptor is defined by the structure [https://www-soc.lip6.fr/trac/almos-mkh/browser/trunk/kernel/mm/vseg.h#L72 vseg_t].
    1717
    1818For each process P, the process descriptor is replicated in all clusters containing at least one thread of P, and these clusters are called active clusters. More precisely, the virtual memory manager VMM(P,K) of process P in active cluster K, contains two main structures:
    19  * The VSL(P,K) is the list of all vsegs registered for process P in cluster K,
    20  * The GPT(P,K) is the generic page table, defining the actual physical mapping of those vsegs.
     19 * The [https://www-soc.lip6.fr/trac/almos-mkh/browser/trunk/kernel/mm/vmm.h#L108 VSL(P,K)] is the list of all vsegs registered for process P in cluster K,
     20 * The [https://www-soc.lip6.fr/trac/almos-mkh/browser/trunk/kernel/mm/vmm.h#L111 GPT(P,K)] is the generic page table, defining the actual physical mapping of those vsegs.
    2121
    2222== __1)  User segments types and attributes__  ==
     
    3838 1. '''DATA''' : This vseg contains the user application global data. ALMOS-MK creates one single DATA vseg per process, that is registered in the reference VSL(P,Z) when the process P is created in reference cluster Z.  In the other clusters X, the DATA vseg is registered  in VSL(P,X) when a page fault is signaled by a thread of P running in cluster X. To avoid contention, this vseg is physically distributed on all clusters, with a page granularity. For each page, the physical mapping is defined by the LSB bits of the page VPN.
    3939 1. '''STACK''' : This private vseg contains the execution stack of a thread. For each thread T of process P running in cluster X, ALMOS_MK creates one STACK vseg. This vseg is registered in the VSL(P,X) when the thread descriptor is created in cluster X. To enforce locality, this vseg is physically mapped in cluster X.
    40  1. '''ANON''' : This type of vseg is dynamically created by ALMOS-MK to serve an anonymous mmap() system call executed by a client thread running in a cluster X. The first vseg registration and the physical mapping are done by the reference cluster Z, but the vseg is mapped in the client cluster X.
     40 1. '''ANON''' : This type of vseg is dynamically created by ALMOS-MK to serve an anonymous [https://www-soc.lip6.fr/trac/almos-mkh/browser/trunk/kernel/syscalls/sys_mmap.c#L38 mmap()] system call executed by a client thread running in a cluster X. The first vseg registration and the physical mapping are done by the reference cluster Z, but the vseg is mapped in the client cluster X.
    4141 1. '''FILE''' : This type of vseg is dynamically created by ALMOS-MK to serve a file based mmap() system call executed by a client thread running in a cluster X. The first vseg registration and the physical mapping are done by the reference cluster Z, but the vseg is mapped in cluster Y containing the file cache.
    4242 1. '''REMOTE''' : This type of vseg is dynamically created by ALMOS-MK to serve a remote mmap() system call where a client thread running in a cluster X requests to create a new vseg mapped in another cluster Y. The first vseg registration and the physical mapping are done by the reference cluster Z, but the vseg is mapped in cluster Y specified by the user.
     
    5353== __2) User process virtual space organisation__ ==
    5454
    55 The virtual address space of a user process P is split in 4 fixed size zones, defined by configuration parameters.  Each zone contains one or several vsegs, as described below.
     55The virtual address space of a user process P is split in 4 fixed size zones, defined by configuration parameters in [https://www-soc.lip6.fr/trac/almos-mkh/browser/trunk/kernel/kernel_config.h#L289 kernel_config.h].  Each zone contains one or several vsegs, as described below.
    5656
    5757=== The ''utils'' zone ===
    58 It is located in the lower part of the virtual space, and starts a address 0. It contains the three vsegs ''kentry'', ''args'', ''envs'', whose sizes are defined by specific configuration parameters
     58It is located in the lower part of the virtual space, and starts a address 0. It contains the three vsegs ''kentry'', ''args'', ''envs'', whose sizes are defined by [https://www-soc.lip6.fr/trac/almos-mkh/browser/trunk/kernel/kernel_config.h#L300 specific configuration parameters]
    5959 * The ''kentry'' vseg (CODE type) contains the HAL specific code that must be executed to enter/exit the kernel from user space (in case of interrupts, exceptions, or syscalls). It also contains the HAL specific code for context switches. For some architectures (namely the TSAR 32 bits architectures), this vseg must be identity mapped.
    6060 * The ''args'' vseg (DATA type) contains the process main() arguments.
     
    6262
    6363=== The ''elf'' zone ===
    64 It is located on top of the '''utils''' zone, and starts at address defined by the CONFIG_VSPACE_ELF_BASE parameter. It contains the ''text'' (CODE type) and ''data'' (DATA type) vsegs, defining the process binary code and global data. The actual vsegs base addresses and sizes are defined in the .elf file and reported in the boot_info structure by the boot loader.
     64It is located on top of the '''utils''' zone, and starts at address defined by the [https://www-soc.lip6.fr/trac/almos-mkh/browser/trunk/kernel/kernel_config.h#L296 CONFIG_VMM_ELF_BASE] parameter. It contains the ''text'' (CODE type) and ''data'' (DATA type) vsegs, defining the process binary code and global data. The actual vsegs base addresses and sizes are defined in the .elf file and reported in the boot_info structure by the boot loader.
    6565
    6666=== The ''heap'' zone ===
    67 It is located on top of the '''elf''' zone, and starts at the address defined by the CONFIG_VSPACE_HEAP_BASE  parameter. It contains all vsegs dynamically allocated / released  by the mmap() / munmap() system calls (i.e. FILE / ANON / REMOTE types). The VMM implements a specific MMAP allocator for this zone, implementing the ''buddy'' algorithm. The mmap( FILE ) syscall maps directly a file in user space. The user level ''malloc'' library uses the mmap( ANON ) syscall to allocate virtual memory from the heap and map it in the same cluster as the calling thread. Besides the standard malloc() function, this library implements a non-standard remote_malloc() function, that uses the mmap( REMOTE ) syscall to dynamically allocate virtual memory from the heap, and map it to a remote physical cluster. 
     67It is located on top of the '''elf''' zone, and starts at the address defined by the [https://www-soc.lip6.fr/trac/almos-mkh/browser/trunk/kernel/kernel_config.h#L297 CONFIG_VMM_HEAP_BASE]  parameter. It contains all vsegs dynamically allocated / released  by the [https://www-soc.lip6.fr/trac/almos-mkh/browser/trunk/kernel/syscalls/sys_mmap.c#L38 mmap()] / [https://www-soc.lip6.fr/trac/almos-mkh/browser/trunk/kernel/syscalls/sys_munmap.c#L37 munmap()] system calls (i.e. FILE / ANON / REMOTE types). The VMM implements a specific MMAP allocator for this zone, implementing the ''buddy'' algorithm. The mmap( FILE ) syscall maps directly a file in user space. The user level ''malloc'' library uses the mmap( ANON ) syscall to allocate virtual memory from the heap and map it in the same cluster as the calling thread. Besides the standard malloc() function, this library implements a non-standard [https://www-soc.lip6.fr/trac/almos-mkh/browser/trunk/libs/libalmosmkh/almosmkh.c#L581 remote_malloc()] function, that uses the mmap( REMOTE ) syscall to dynamically allocate virtual memory from the heap, and map it to a remote physical cluster. 
    6868
    6969=== The ''stack'' zone ===
    70 It is located on top of the '''mmap''' zone and starts at the address defined by the CONFIG_VSPACE_STACK_BASE parameter. It contains an array of fixed size slots, and each slot contains one ''stack'' vseg. The size of a slot is defined by the CONFIG_VSPACE_STACK_SIZE. In each slot, the first page is not mapped, in order to detect stack overflows. As threads are dynamically created and destroyed, the VMM implements a specific STACK allocator for this zone, using a bitmap vector. As the ''stack'' vsegs are private (the same virtual address can have different mappings, depending on the cluster) the number of slots in the '''stack''' zone actually defines the max number of threads for given process in a given cluster.
     70It is located on top of the '''mmap''' zone and starts at the address defined by the [https://www-soc.lip6.fr/trac/almos-mkh/browser/trunk/kernel/kernel_config.h#L298 CONFIG_VMM_STACK_BASE] parameter. It contains an array of fixed size slots, and each slot contains one ''stack'' vseg. The size of a slot is defined by the [https://www-soc.lip6.fr/trac/almos-mkh/browser/trunk/kernel/kernel_config.h#L303 CONFIG_VMM_STACK_SIZE]. In each slot, the first page is not mapped, in order to detect stack overflows. As threads are dynamically created and destroyed, the VMM implements a specific STACK allocator for this zone, using a bitmap vector. As the ''stack'' vsegs are private (the same virtual address can have different mappings, depending on the cluster) the number of slots in the '''stack''' zone actually defines the max number of threads for given process in a given cluster.