Some time ago, Hrvoje Niksic wrote... |+ | sperber(a)informatik.uni-tuebingen.de (Michael Sperber [Mr. Preprocessor]) writes: | | > On another note, is a full stat really necessary on NT to compute | > file-directory-p? | | Good question. Note, however, that I am not running on NT. |- stat() C library call ends up with FindFirstFile, the API which starts enumeration of files matching pattern in a directory. Since stats in package search case usually come short after listing directory, they must be pretty cheap for the information is already cached by the system. The same applies to network shares, becuause rdr caches network drives very intelligently, if underlying protocol allows (SMB does). Do not know about '95 though. Kirill

Some time ago, Darryl Okahata wrote... |+ | I don't know about NT, but stat() is VERY expensive under Win95. | If I recall correctly, a call to stat() takes on the order of | milliseconds on a non-MMX P166 (and I think over 10ms), under Win95 | OSR2. Why, I don't know (this is real/elapsed, and not CPU, time). By | bypassing stat(), and using the native Win32 system calls, my dired-in-C | changes were able to get a significant performance improvement. |- Ok, I wrote a simple statometer. On my system (P133 64MB NT 4.0 SP3) it averages to around 800 us per stat call. 398 stats in 325 ms, 818 us per call 398 stats in 325 ms, 818 us per call 398 stats in 328 ms, 824 us per call 398 stats in 328 ms, 824 us per call 398 stats in 325 ms, 819 us per call Generally this means that XEmacs spends almost 2 seconds in stats on statup, if it counts to 2,000 stats. Here's a source, perhaps useless outside of win32 world. Anybody's out to port this on UNIX? #include <windows.h> #include <stdio.h> #include <sys/types.h> #include <sys/stat.h> void main () { LARGE_INTEGER start, end, res; LONGLONG time = 0; int ncalls = 0; WIN32_FIND_DATA wfd; struct stat statbuf; HANDLE hf = FindFirstFile ("*", &wfd); if (hf) do { QueryPerformanceCounter (&start); stat (wfd.cFileName, &statbuf); QueryPerformanceCounter (&end); time += end.QuadPart - start.QuadPart; ++ncalls; } while (FindNextFile (hf, &wfd)); QueryPerformanceFrequency (&res); printf ("%d stats in %ld ms, %ld us per call\n", ncalls, (long)(time * 1000 / res.QuadPart), (long)(time * 1000000 / ncalls / res.QuadPart)); }

Some time ago, Darryl Okahata wrote... |+ | "Kirill M. Katsnelson" <kkm(a)kis.ru&gt; wrote: | | > Ok, I wrote a simple statometer. On my system (P133 64MB NT 4.0 SP3) it | > averages to around 800 us per stat call. | | The cost is related to the number of files in the directory, at | least under Win95. On my system (non-MMX P166, 512KB L2 cache, 64MB | RAM), the program gives: | | 435 stats in 1590 ms, 3655 us per call | 1215 stats in 9156 ms, 7536 us per call |- I see this growth on FAT volumes and cd roms, but not on NTFS volumes: NTFS drive: 8 stats in 7 ms, 897 us per call 398 stats in 318 ms, 799 us per call 2481 stats in 2041 ms, 822 us per call FAT drive: 9 stats in 8 ms, 922 us per call 54 stats in 43 ms, 802 us per call 679 stats in 678 ms, 999 us per call 1291 stats in 1595 ms, 1235 us per call CD rom: 42 stats in 132 ms, 3154 us per call 789 stats in 5917 ms, 7500 us per call Kirill