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• Client-Server MMOG & data structures sync when joining / playing

  - by plang

  After reading a few articles on MMOG architecture, there is still one point on which I cannot find much information: it has to do with how you keep in sync server data on the client, when you join, and while you play. A pretty vague question, I agree. Let me refine it: Let's say we have an MMOG virtual world subdivided into geographical cells. A player in a cell is mostly interested in what happens in the cell itself, and all the surrounding cells, not more. When joining the game for the first time, the only thing we can do is send some sort of "database dump" of the interesting cells to the client. When playing, I guess it would be very inefficient to do the same thing regularly. I imagine the best thing to do is to send "deltas" to the client, which would allow keeping the local database in sync. Now let's say the player moves, and arrives in another cell. Surrounding cells change, and for all the new cells the player subscribes, the same technique as used when joining the game has to be used: some sort of "database dump". This mechanic of joining/moving in a cell-based MMOG virtual world interests me, and I was wondering if there were tried and tested techniques in this domain. Thanks!

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• Shell command slow when using pipe, fast with intermediate file

  - by plang

  Does anyone understand this huge difference in processing time, when using an intermediate file, or when using a pipe? I'm converting tiff to pdf using standard tools on a fresh debian squeeze server. A standard way of doing this is to convert to ps first. Without pipe: root@web5:~# time tiff2ps test.tif > test.ps real 0m0.860s user 0m0.744s sys 0m0.112s root@web5:~# time ps2pdf13 -sPAPERSIZE=a4 test.ps > test.pdf real 0m0.667s user 0m0.612s sys 0m0.060s With pipe: root@web5:~# time tiff2ps test.tif | ps2pdf13 -sPAPERSIZE=a4 - > test.pdf real 1m6.098s user 0m15.861s sys 0m50.9 During the last command, gs process is at 100% all the time. Update: Here is an strace output for the ps generation: root@web5:~# strace tiff2ps test.tif > test.ps execve("/usr/bin/tiff2ps", ["tiff2ps", "test.tif"], [/* 28 vars */]) = 0 brk(0) = 0x1395000 access("/etc/ld.so.nohwcap", F_OK) = -1 ENOENT (No such file or directory) mmap(NULL, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7fb5a1937000 access("/etc/ld.so.preload", R_OK) = -1 ENOENT (No such file or directory) open("/etc/ld.so.cache", O_RDONLY) = 3 fstat(3, {st_mode=S_IFREG|0644, st_size=21735, ...}) = 0 mmap(NULL, 21735, PROT_READ, MAP_PRIVATE, 3, 0) = 0x7fb5a1931000 close(3) = 0 access("/etc/ld.so.nohwcap", F_OK) = -1 ENOENT (No such file or directory) open("/usr/lib/libtiff.so.4", O_RDONLY) = 3 read(3, "\177ELF\2\1\1\0\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0P\200\0\0\0\0\0\0"..., 832) = 832 fstat(3, {st_mode=S_IFREG|0644, st_size=405128, ...}) = 0 mmap(NULL, 2501416, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x7fb5a14b9000 mprotect(0x7fb5a151a000, 2093056, PROT_NONE) = 0 mmap(0x7fb5a1719000, 12288, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x60000) = 0x7fb5a1719000 close(3) = 0 access("/etc/ld.so.nohwcap", F_OK) = -1 ENOENT (No such file or directory) open("/usr/lib/libjpeg.so.62", O_RDONLY) = 3 read(3, "\177ELF\2\1\1\0\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0\3408\0\0\0\0\0\0"..., 832) = 832 fstat(3, {st_mode=S_IFREG|0644, st_size=145048, ...}) = 0 mmap(NULL, 2240080, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x7fb5a1296000 mprotect(0x7fb5a12b9000, 2093056, PROT_NONE) = 0 mmap(0x7fb5a14b8000, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x22000) = 0x7fb5a14b8000 close(3) = 0 access("/etc/ld.so.nohwcap", F_OK) = -1 ENOENT (No such file or directory) open("/usr/lib/libz.so.1", O_RDONLY) = 3 read(3, "\177ELF\2\1\1\0\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0\260\"\0\0\0\0\0\0"..., 832) = 832 fstat(3, {st_mode=S_IFREG|0644, st_size=93936, ...}) = 0 mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7fb5a1930000 mmap(NULL, 2188976, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x7fb5a107f000 mprotect(0x7fb5a1096000, 2093056, PROT_NONE) = 0 mmap(0x7fb5a1295000, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x16000) = 0x7fb5a1295000 close(3) = 0 access("/etc/ld.so.nohwcap", F_OK) = -1 ENOENT (No such file or directory) open("/lib/libm.so.6", O_RDONLY) = 3 read(3, "\177ELF\2\1\1\0\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0\360>\0\0\0\0\0\0"..., 832) = 832 fstat(3, {st_mode=S_IFREG|0644, st_size=530736, ...}) = 0 mmap(NULL, 2625768, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x7fb5a0dfd000 mprotect(0x7fb5a0e7d000, 2097152, PROT_NONE) = 0 mmap(0x7fb5a107d000, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x80000) = 0x7fb5a107d000 close(3) = 0 access("/etc/ld.so.nohwcap", F_OK) = -1 ENOENT (No such file or directory) open("/lib/libc.so.6", O_RDONLY) = 3 read(3, "\177ELF\2\1\1\0\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0\240\355\1\0\0\0\0\0"..., 832) = 832 fstat(3, {st_mode=S_IFREG|0755, st_size=1437064, ...}) = 0 mmap(NULL, 3545160, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x7fb5a0a9b000 mprotect(0x7fb5a0bf4000, 2093056, PROT_NONE) = 0 mmap(0x7fb5a0df3000, 20480, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x158000) = 0x7fb5a0df3000 mmap(0x7fb5a0df8000, 18504, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0x7fb5a0df8000 close(3) = 0 mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7fb5a192f000 mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7fb5a192e000 mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7fb5a192d000 arch_prctl(ARCH_SET_FS, 0x7fb5a192e700) = 0 mprotect(0x7fb5a0df3000, 16384, PROT_READ) = 0 mprotect(0x7fb5a107d000, 4096, PROT_READ) = 0 mprotect(0x7fb5a1939000, 4096, PROT_READ) = 0 munmap(0x7fb5a1931000, 21735) = 0 open("test.tif", O_RDONLY) = 3 brk(0) = 0x1395000 brk(0x13b6000) = 0x13b6000 read(3, "II*\0\10\0\0\0", 8) = 8 fstat(3, {st_mode=S_IFREG|0644, st_size=1825656, ...}) = 0 mmap(NULL, 1825656, PROT_READ, MAP_SHARED, 3, 0) = 0x7fb5a176f000 open("/proc/meminfo", O_RDONLY) = 4 fstat(4, {st_mode=S_IFREG|0444, st_size=0, ...}) = 0 mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7fb5a1936000 read(4, "MemTotal: 2090844 kB\nMemF"..., 1024) = 1024 close(4) = 0 munmap(0x7fb5a1936000, 4096) = 0 write(2, "TIFFReadDirectory: ", 19TIFFReadDirectory: ) = 19 write(2, "Warning, ", 9Warning, ) = 9 write(2, "test.tif: wrong data type 7 for "..., 59test.tif: wrong data type 7 for "RichTIFFIPTC"; tag ignored) = 59 write(2, ".\n", 2. ) = 2 gettimeofday({1334836895, 374666}, NULL) = 0 fstat(1, {st_mode=S_IFREG|0664, st_size=0, ...}) = 0 mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7fb5a1936000 open("/etc/localtime", O_RDONLY) = 4 fstat(4, {st_mode=S_IFREG|0644, st_size=1892, ...}) = 0 fstat(4, {st_mode=S_IFREG|0644, st_size=1892, ...}) = 0 mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7fb5a1935000 read(4, "TZif2\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\4\0\0\0\4\0\0\0\0"..., 4096) = 1892 lseek(4, -1217, SEEK_CUR) = 675 read(4, "TZif2\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\6\0\0\0\6\0\0\0\0"..., 4096) = 1217 close(4) = 0 munmap(0x7fb5a1935000, 4096) = 0 write(1, "%!PS-Adobe-3.0 EPSF-3.0\n%%Creato"..., 4096) = 4096 write(1, "fffffffffffffffffffffffffffff\nff"..., 4096) = 4096 write(1, "ffffffffffffffffffff\nfffffffffff"..., 4096) = 4096 write(1, "fffffffffff\nffffffffffffffffffff"..., 4096) = 4096 write(1, "ff\nfffffffffffffffffffffffffffff"..., 4096) = 4096 write(1, "ffffffffffffffffffffffffffffffff"..., 4096) = 4096 write(1, "ffffffffffffffffffffffffffffffff"..., 4096) = 4096 write(1, "ffffffffffffffffffffffffffffffff"..., 4096) = 4096 write(1, "ffffffffffffffffffffffffffffffff"..., 4096) = 4096 write(1, "ffffffffffffffffffffffff\nfffffff"..., 4096) = 4096 Here is an strace output for the piped version: PS generation seems to be much slower when output is piped into ps2pdf13. root@web5:~# strace tiff2ps test.tif | ps2pdf13 -sPAPERSIZE=a4 - > test.pdf execve("/usr/bin/tiff2ps", ["tiff2ps", "test.tif"], [/* 28 vars */]) = 0 brk(0) = 0x1b97000 access("/etc/ld.so.nohwcap", F_OK) = -1 ENOENT (No such file or directory) mmap(NULL, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f9208bb1000 access("/etc/ld.so.preload", R_OK) = -1 ENOENT (No such file or directory) open("/etc/ld.so.cache", O_RDONLY) = 3 fstat(3, {st_mode=S_IFREG|0644, st_size=21735, ...}) = 0 mmap(NULL, 21735, PROT_READ, MAP_PRIVATE, 3, 0) = 0x7f9208bab000 close(3) = 0 access("/etc/ld.so.nohwcap", F_OK) = -1 ENOENT (No such file or directory) open("/usr/lib/libtiff.so.4", O_RDONLY) = 3 read(3, "\177ELF\2\1\1\0\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0P\200\0\0\0\0\0\0"..., 832) = 832 fstat(3, {st_mode=S_IFREG|0644, st_size=405128, ...}) = 0 mmap(NULL, 2501416, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x7f9208733000 mprotect(0x7f9208794000, 2093056, PROT_NONE) = 0 mmap(0x7f9208993000, 12288, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x60000) = 0x7f9208993000 close(3) = 0 access("/etc/ld.so.nohwcap", F_OK) = -1 ENOENT (No such file or directory) open("/usr/lib/libjpeg.so.62", O_RDONLY) = 3 read(3, "\177ELF\2\1\1\0\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0\3408\0\0\0\0\0\0"..., 832) = 832 fstat(3, {st_mode=S_IFREG|0644, st_size=145048, ...}) = 0 mmap(NULL, 2240080, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x7f9208510000 mprotect(0x7f9208533000, 2093056, PROT_NONE) = 0 mmap(0x7f9208732000, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x22000) = 0x7f9208732000 close(3) = 0 access("/etc/ld.so.nohwcap", F_OK) = -1 ENOENT (No such file or directory) open("/usr/lib/libz.so.1", O_RDONLY) = 3 read(3, "\177ELF\2\1\1\0\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0\260\"\0\0\0\0\0\0"..., 832) = 832 fstat(3, {st_mode=S_IFREG|0644, st_size=93936, ...}) = 0 mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f9208baa000 mmap(NULL, 2188976, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x7f92082f9000 mprotect(0x7f9208310000, 2093056, PROT_NONE) = 0 mmap(0x7f920850f000, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x16000) = 0x7f920850f000 close(3) = 0 access("/etc/ld.so.nohwcap", F_OK) = -1 ENOENT (No such file or directory) open("/lib/libm.so.6", O_RDONLY) = 3 read(3, "\177ELF\2\1\1\0\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0\360>\0\0\0\0\0\0"..., 832) = 832 fstat(3, {st_mode=S_IFREG|0644, st_size=530736, ...}) = 0 mmap(NULL, 2625768, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x7f9208077000 mprotect(0x7f92080f7000, 2097152, PROT_NONE) = 0 mmap(0x7f92082f7000, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x80000) = 0x7f92082f7000 close(3) = 0 access("/etc/ld.so.nohwcap", F_OK) = -1 ENOENT (No such file or directory) open("/lib/libc.so.6", O_RDONLY) = 3 read(3, "\177ELF\2\1\1\0\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0\240\355\1\0\0\0\0\0"..., 832) = 832 fstat(3, {st_mode=S_IFREG|0755, st_size=1437064, ...}) = 0 mmap(NULL, 3545160, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x7f9207d15000 mprotect(0x7f9207e6e000, 2093056, PROT_NONE) = 0 mmap(0x7f920806d000, 20480, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x158000) = 0x7f920806d000 mmap(0x7f9208072000, 18504, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0x7f9208072000 close(3) = 0 mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f9208ba9000 mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f9208ba8000 mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f9208ba7000 arch_prctl(ARCH_SET_FS, 0x7f9208ba8700) = 0 mprotect(0x7f920806d000, 16384, PROT_READ) = 0 mprotect(0x7f92082f7000, 4096, PROT_READ) = 0 mprotect(0x7f9208bb3000, 4096, PROT_READ) = 0 munmap(0x7f9208bab000, 21735) = 0 open("test.tif", O_RDONLY) = 3 brk(0) = 0x1b97000 brk(0x1bb8000) = 0x1bb8000 read(3, "II*\0\10\0\0\0", 8) = 8 fstat(3, {st_mode=S_IFREG|0644, st_size=1825656, ...}) = 0 mmap(NULL, 1825656, PROT_READ, MAP_SHARED, 3, 0) = 0x7f92089e9000 open("/proc/meminfo", O_RDONLY) = 4 fstat(4, {st_mode=S_IFREG|0444, st_size=0, ...}) = 0 mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f9208bb0000 read(4, "MemTotal: 2090844 kB\nMemF"..., 1024) = 1024 close(4) = 0 munmap(0x7f9208bb0000, 4096) = 0 write(2, "TIFFReadDirectory: ", 19TIFFReadDirectory: ) = 19 write(2, "Warning, ", 9Warning, ) = 9 write(2, "test.tif: wrong data type 7 for "..., 59test.tif: wrong data type 7 for "RichTIFFIPTC"; tag ignored) = 59 write(2, ".\n", 2. ) = 2 gettimeofday({1334836513, 114140}, NULL) = 0 fstat(1, {st_mode=S_IFIFO|0600, st_size=0, ...}) = 0 mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f9208bb0000 open("/etc/localtime", O_RDONLY) = 4 fstat(4, {st_mode=S_IFREG|0644, st_size=1892, ...}) = 0 fstat(4, {st_mode=S_IFREG|0644, st_size=1892, ...}) = 0 mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f9208baf000 read(4, "TZif2\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\4\0\0\0\4\0\0\0\0"..., 4096) = 1892 lseek(4, -1217, SEEK_CUR) = 675 read(4, "TZif2\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\6\0\0\0\6\0\0\0\0"..., 4096) = 1217 close(4) = 0 munmap(0x7f9208baf000, 4096) = 0 write(1, "%!PS-Adobe-3.0 EPSF-3.0\n%%Creato"..., 4096) = 4096 write(1, "fffffffffffffffffffffffffffff\nff"..., 4096) = 4096 write(1, "ffffffffffffffffffff\nfffffffffff"..., 4096) = 4096 write(1, "fffffffffff\nffffffffffffffffffff"..., 4096) = 4096 write(1, "ff\nfffffffffffffffffffffffffffff"..., 4096) = 4096 write(1, "ffffffffffffffffffffffffffffffff"..., 4096) = 4096 write(1, "ffffffffffffffffffffffffffffffff"..., 4096) = 4096 write(1, "ffffffffffffffffffffffffffffffff"..., 4096) = 4096 write(1, "ffffffffffffffffffffffffffffffff"..., 4096) = 4096 ...etc...

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