Hello,
Egy kedves ismerosom keresett meg egy kerdessel, de nem tudtam neki valaszolni, hatha itt valaki tud segiteni! (bocsanat, angolul van) What is the meaning of dirty_expire_centisecs ? The most authentic-looking info I have found is in https://www.kernel.org/doc/Documentation/sysctl/vm.txt dirty_expire_centisecs This tunable is used to define when dirty data is old enough to be eligible for writeout by the kernel flusher threads. It is expressed in 100'ths of a second. Data which has been dirty in-memory for longer than this interval will be written out next time a flusher thread wakes up. That can be read in two different ways: - persistence is "guaranteed" (modulo system load, disk spinned down etc) to happen in dirty_expire_centisecs + dirty_writeback_centisecs - the other reading is that if a page wasn't updated in dirty_expire_centisecs, it'll be persisted at most dirty_writeback_centisecs after that, but if it is being written regularly, no persistence ever happens (at least not by the flusher thread) I'd think the latter is the correct reading: this is a performance tuning optimization for the filesystem cache - the OS doesn't want to generate unnecessary I/O by persisting pages that keep changing, but it can be beneficial not to hold back all writes creating a bottleneck for later, so pages that no longer seem to be written get persisted in the background. Did try to find the corresponding code with no luck, a pointer would be appreciated! koszi Szo _________________________________________________ linux lista - linux@mlf.linux.rulez.org http://mlf.linux.rulez.org/mailman/listinfo/linux
