1 /* Copyright (c) 2015-2017. The SimGrid Team. All rights reserved. */
3 /* This program is free software; you can redistribute it and/or modify it
4 * under the terms of the license (GNU LGPL) which comes with this package. */
13 #include <sys/types.h>
24 #include "src/xbt/memory_map.hpp"
26 #include "src/smpi/private.h"
27 #include "private.hpp"
29 XBT_LOG_NEW_DEFAULT_SUBCATEGORY(smpi_memory, smpi, "Memory layout support for SMPI");
31 int smpi_loaded_page = -1;
32 char* smpi_start_data_exe = nullptr;
33 int smpi_size_data_exe = 0;
34 int smpi_privatize_global_variables;
36 static const int PROT_RWX = (PROT_READ | PROT_WRITE | PROT_EXEC);
37 static const int PROT_RW = (PROT_READ | PROT_WRITE );
38 XBT_ATTRIB_UNUSED static const int PROT_RX = (PROT_READ | PROT_EXEC );
40 void smpi_get_executable_global_size()
42 char buffer[PATH_MAX];
43 char* full_name = realpath(xbt_binary_name, buffer);
44 if (full_name == nullptr)
45 xbt_die("Could not resolve binary file name");
47 std::vector<simgrid::xbt::VmMap> map = simgrid::xbt::get_memory_map(getpid());
48 for (auto i = map.begin(); i != map.end() ; ++i) {
49 // TODO, In practice, this implementation would not detect a completely
50 // anonymous data segment. This does not happen in practice, however.
52 // File backed RW entry:
53 if (i->pathname == full_name && (i->prot & PROT_RWX) == PROT_RW) {
54 smpi_start_data_exe = (char*) i->start_addr;
55 smpi_size_data_exe = i->end_addr - i->start_addr;
57 /* Here we are making the assumption that a suitable empty region
58 following the rw- area is the end of the data segment. It would
59 be better to check with the size of the data segment. */
60 if (i != map.end() && i->pathname.empty() && (i->prot & PROT_RWX) == PROT_RW
61 && (char*)i->start_addr == smpi_start_data_exe + smpi_size_data_exe) {
62 smpi_size_data_exe = (char*)i->end_addr - smpi_start_data_exe;
67 xbt_die("Did not find my data segment.");
72 /** Map a given SMPI privatization segment (make a SMPI process active) */
73 void smpi_switch_data_segment(int dest) {
74 if (smpi_loaded_page == dest)//no need to switch, we've already loaded the one we want
78 smpi_really_switch_data_segment(dest);
81 /** Map a given SMPI privatization segment (make a SMPI process active) even if SMPI thinks it is already active
83 * When doing a state restoration, the state of the restored variables might not be consistent with the state of the
84 * virtual memory. In this case, we to change the data segment.
86 void smpi_really_switch_data_segment(int dest)
88 if(smpi_size_data_exe == 0)//no need to switch
91 #if HAVE_PRIVATIZATION
92 if(smpi_loaded_page==-1){//initial switch, do the copy from the real page here
93 for (int i=0; i< smpi_process_count(); i++){
94 memcpy(smpi_privatisation_regions[i].address, TOPAGE(smpi_start_data_exe), smpi_size_data_exe);
98 // FIXME, cross-process support (mmap across process when necessary)
99 int current = smpi_privatisation_regions[dest].file_descriptor;
100 XBT_DEBUG("Switching data frame to the one of process %d", dest);
102 mmap(TOPAGE(smpi_start_data_exe), smpi_size_data_exe, PROT_READ | PROT_WRITE, MAP_FIXED | MAP_SHARED, current, 0);
103 if (tmp != TOPAGE(smpi_start_data_exe))
104 xbt_die("Couldn't map the new region (errno %d): %s", errno, strerror(errno));
105 smpi_loaded_page = dest;
109 int smpi_is_privatisation_file(char* file)
111 return strncmp("/dev/shm/my-buffer-", file, std::strlen("/dev/shm/my-buffer-")) == 0;
114 void smpi_initialize_global_memory_segments()
117 #if HAVE_PRIVATIZATION
118 smpi_get_executable_global_size();
120 XBT_DEBUG ("bss+data segment found : size %d starting at %p", smpi_size_data_exe, smpi_start_data_exe );
122 if (smpi_size_data_exe == 0){//no need to switch
123 smpi_privatize_global_variables=false;
127 smpi_privatisation_regions = static_cast<smpi_privatisation_region_t>(
128 xbt_malloc(smpi_process_count() * sizeof(struct s_smpi_privatisation_region)));
130 for (int i=0; i< smpi_process_count(); i++){
131 // create SIMIX_process_count() mappings of this size with the same data inside
133 void* address = nullptr;
138 snprintf(path, sizeof(path), "/smpi-buffer-%06x", rand() % 0xffffff);
139 file_descriptor = shm_open(path, O_RDWR | O_CREAT | O_EXCL, S_IRUSR | S_IWUSR);
140 } while (file_descriptor == -1 && errno == EEXIST);
141 if (file_descriptor < 0) {
142 if (errno == EMFILE) {
143 xbt_die("Impossible to create temporary file for memory mapping: %s\n\
144 The open() system call failed with the EMFILE error code (too many files). \n\n\
145 This means that you reached the system limits concerning the amount of files per process. \
146 This is not a surprise if you are trying to virtualize many processes on top of SMPI. \
147 Don't panic -- you should simply increase your system limits and try again. \n\n\
148 First, check what your limits are:\n\
149 cat /proc/sys/fs/file-max # Gives you the system-wide limit\n\
150 ulimit -Hn # Gives you the per process hard limit\n\
151 ulimit -Sn # Gives you the per process soft limit\n\
152 cat /proc/self/limits # Displays any per-process limitation (including the one given above)\n\n\
153 If one of these values is less than the amount of MPI processes that you try to run, then you got the explanation of this error. \
154 Ask the Internet about tutorials on how to increase the files limit such as: https://rtcamp.com/tutorials/linux/increase-open-files-limit/",
157 xbt_die("Impossible to create temporary file for memory mapping: %s", strerror(errno));
160 status = ftruncate(file_descriptor, smpi_size_data_exe);
162 xbt_die("Impossible to set the size of the temporary file for memory mapping");
164 /* Ask for a free region */
165 address = mmap(nullptr, smpi_size_data_exe, PROT_READ | PROT_WRITE, MAP_SHARED, file_descriptor, 0);
166 if (address == MAP_FAILED)
167 xbt_die("Couldn't find a free region for memory mapping");
169 status = shm_unlink(path);
171 xbt_die("Impossible to unlink temporary file for memory mapping");
173 // initialize the values
174 memcpy(address, TOPAGE(smpi_start_data_exe), smpi_size_data_exe);
176 // store the address of the mapping for further switches
177 smpi_privatisation_regions[i].file_descriptor = file_descriptor;
178 smpi_privatisation_regions[i].address = address;
180 #else /* ! HAVE_PRIVATIZATION */
181 smpi_privatize_global_variables = false;
182 xbt_die("You are trying to use privatization on a system that does not support it. Don't.");
187 void smpi_destroy_global_memory_segments(){
188 if (smpi_size_data_exe == 0)//no need to switch
190 #if HAVE_PRIVATIZATION
191 for (int i=0; i< smpi_process_count(); i++) {
192 if (munmap(smpi_privatisation_regions[i].address, smpi_size_data_exe) < 0)
193 XBT_WARN("Unmapping of fd %d failed: %s", smpi_privatisation_regions[i].file_descriptor, strerror(errno));
194 close(smpi_privatisation_regions[i].file_descriptor);
196 xbt_free(smpi_privatisation_regions);