/* * Mausezahn - A fast versatile traffic generator * Copyright (C) 2008-2010 Herbert Haas * * This program is free software; you can redistribute it and/or modify it under * the terms of the GNU General Public License version 2 as published by the * Free Software Foundation. * * This program is distributed in the hope that it will be useful, but WITHOUT * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS * FOR A PARTICULAR PURPOSE. See the GNU General Public License for more * details. * * You should have received a copy of the GNU General Public License along with * this program; if not, see http://www.gnu.org/licenses/gpl-2.0.html * */ #include "mz.h" // Check if current system supports the nanosecond timer functions. // Additionally, measure the precision. // This function should be called upon program start. // int check_timer() { struct timespec res; int r; // Check if the glibc is recent enough: #ifdef _POSIX_C_SOURCE if (_POSIX_C_SOURCE >= 199309L) { r = clock_getres(CLOCK_MONOTONIC, &res); if (r!=0) perror(" mz/check_timer:"); if (verbose) { fprintf(stderr, " This system supports a high resolution clock.\n"); fprintf(stderr, " The clock resolution is %li nanoseconds.\n", res.tv_nsec); } } else { fprintf(stderr, " WARNING: Your system does NOT support the newer high resolution clock\n" " Please inform the author: herbert@perihel.at\n"); exit(1); } #endif return 0; } // This is the replacement for gettimeofday() which would result in 'jumps' if // the system clock is adjusted (e. g. via a NTP process) and finally the jitter // measurement would include wrong datapoints. // // Furthermore the function below utilizes the newer hi-res nanosecond timers. inline void getcurtime (struct mz_timestamp *t) { struct timespec ct; clock_gettime(CLOCK_MONOTONIC, &ct); t->sec = ct.tv_sec; t->nsec = ct.tv_nsec; } ////////////////////////////////////////////////////////////////////////////////////// // Purpose: Calculate time deltas of two timestamps stored in struct timeval. // // Subtract the "struct timeval" values X and Y, storing the result in RESULT, // i. e. X-Y=RESULT. // // RETURN VALUES: // // Sign: 1 = negative, 0 = positive // Error: -1 due to a wrong timestamp (i. e. nsec > 999999999L) // inline int timestamp_subtract (struct mz_timestamp *x, struct mz_timestamp *y, struct mz_timestamp *result) { int32_t ndiff; int sign=0, carry=0; // Check for wrong timestamps if ((x->nsec>999999999L) || (y->nsec>999999999L)) return -1; if (y->sec > x->sec) sign=1; else if ((y->sec == x->sec) && (y->nsec > x->nsec)) sign=1; ndiff = x->nsec - y->nsec; if ((ndiff>0) && (sign)) carry=1; if ((ndiff<0) && (sign)) ndiff = y->nsec - x->nsec; if ((ndiff<0) && (!sign)) { ndiff = 1000000000L + ndiff; carry=1; } if (sign) result->sec = y->sec - x->sec - carry; else result->sec = x->sec - y->sec - carry; result->nsec = ndiff; return sign; } // Add two variables of type struct mz_timestamp: x+y=result. // inline void timestamp_add (struct mz_timestamp *x, struct mz_timestamp *y, struct mz_timestamp *result) { int carry=0; u_int32_t c; c = x->nsec + y->nsec; if (c>999999999L) { carry=1; result->nsec =c-1000000000; } else result->nsec =c; result->sec = x->sec + y->sec + carry; } // Returns a human readable timestamp in the string result. // Optionally a prefix can be specified, for example if the // timestamp is part of a filename. // // Example: // char myTimeStamp[128]; // // timestamp_human(myTimeStamp, NULL); // // => "20080718_155521" // // /* or with prefix */ // // timestamp_human(myTimeStamp, "MZ_RTP_jitter_"); // // => "MZ_RTP_jitter_20080718_155521" // int timestamp_human(char* result, const char* prefix) { time_t curtime; struct tm curtime_broken; char curtime_str[32]; time(&curtime); localtime_r (&curtime, &curtime_broken); sprintf(curtime_str, "%4i%02i%02i-%02i%02i%02i", curtime_broken.tm_year+1900, curtime_broken.tm_mon+1, curtime_broken.tm_mday, curtime_broken.tm_hour, curtime_broken.tm_min, curtime_broken.tm_sec); if (prefix==NULL) { strncpy(result, curtime_str, 32); } else { strncpy(result, prefix, 32); strncat(result, curtime_str, 32); } return 0; } // Creates a human readable timestamp in the string result. // Optionally a prefix can be specified, for example if the // timestamp is part of a filename. // // Example: // char myTimeStamp[9]; // // timestamp_hms (myTimeStamp); // // => "15:55:21" int timestamp_hms(char* result) { time_t curtime; struct tm curtime_broken; char curtime_str[32]; time(&curtime); localtime_r (&curtime, &curtime_broken); sprintf(curtime_str, "%02i:%02i:%02i", curtime_broken.tm_hour, curtime_broken.tm_min, curtime_broken.tm_sec); strncpy(result, curtime_str, 9); return 0; } teback_index point to the last written page
If sequential writer is writing in the middle of the page and it just redirties the last written page by continuing from it. In the above case this can end up with seeking back to that firstly redirtied page after writing all the pages at the end of file because btrfs updates mapping->writeback_index to 1 past the current one. For non-cow filesystems, the cost is only about extra seek, while for cow filesystems such as btrfs, it means unnecessary fragments. To avoid it, we just need to continue writeback from the last written page. This also updates btrfs to behave like what write_cache_pages() does, ie, bail out immediately if there is an error in writepage(). <Ref: https://www.spinics.net/lists/linux-btrfs/msg52628.html> Reported-by: Holger Hoffstätte <holger.hoffstaette@googlemail.com> Signed-off-by: Liu Bo <bo.li.liu@oracle.com> Signed-off-by: David Sterba <dsterba@suse.com>
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