Jan Kara wrote: > On Tue 11-08-09 06:49:20, Al Boldi wrote: > > Theodore Ts'o wrote: > > > + "data=ordered" mode can also result in major performance > > > + problems, including seconds-long delays before an fsync() > > > + call returns. For details, see: > > > + > > > + http://ext4.wiki.kernel.org/index.php/Ext3_data_mode_tradeoffs > > > > Why isn't the fsync problem fixable? > > Because it's quite deep in the design of JBD: All the modifications done > to a filesystem go to one transactions. When the transaction grows big > enough or old enough, we commit the transaction, which means we write all > the metadata to the journal and all the ordered data to their final > location on disk. If you do fsync(), you have to wait for a transaction > commit with your data to finish, so that you are guaranteed a consistent > state of metadata is on disk. But when there is heavy background writing, > it means there's a lot of data you have to write out and wait for... It's > not easy to work around this - naively, you might want to separate out just > the writes you care about for fsync() but that's not easily possible > because bitmaps and group descriptors are modified by other writes as well. Ok, I remember now, that was the konqueror deadlocks problem. I think making the fsync soft in that case would yield a better result than turning ordered-mode off completely. BTW: did you get around fixing the ordered-mode redundant write out problem? Thanks! -- Al -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
