Messages in this thread | | | Date | Thu, 2 Apr 2009 09:33:44 -0700 | Subject | Re: Linux 2.6.29 | From | David Rees <> |
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On Thu, Apr 2, 2009 at 9:09 AM, Andrew Morton <akpm@linux-foundation.org> wrote: > On Thu, 2 Apr 2009 13:05:32 +0200 Janne Grunau <j@jannau.net> wrote: >> MythTV calls fsync every few seconds on ongoing recordings to prevent >> stalls due to large cache writebacks on ext3. > > It should use sync_file_range(SYNC_FILE_RANGE_WRITE). That will > > - have minimum latency. It tries to avoid blocking at all. > - avoid writing metadata > - avoid syncing other unrelated files within ext3 > - avoid waiting for the ext3 commit to complete.
MythTV actually uses fdatasync, not fsync (or at least that's what it did last time I looked at the source). Not sure how the behavior of fdatasync compares to sync_file_range.
Either way - forcing the data to be synced to disk a couple times every second is a hack and causes fragmentation in filesystems without delayed allocation. Fragmentation really goes up if you are recording multiple shows at once.
-Dave -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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