On Jun 16, 2014, at 7:13 PM, cwillu <cwi...@cwillu.com> wrote: > It's not a mmap problem, it's a small writes with an msync or fsync > after each one problem. > > For the case of sequential writes (via write or mmap), padding writes > to page boundaries would help, if the wasted space isn't an issue. > Another approach, again assuming all other writes are appends, would > be to periodically (but frequently enough that the pages are still in > cache) read a chunk of the file and write it back in-place, with or > without an fsync. On the other hand, if you can afford to lose some > logs on a crash, not fsyncing/msyncing after each write will also > eliminate the fragmentation.
Normally I'd be willing to give up ~30 seconds of journal to not have fragmented journals. But then if I use systemd.log_level=debug I'd like that to trigger more frequent flushing to make sure as little of the journaling is lost as possible. Does that make sense? Chris Murphy-- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
