On 02/03 2014 05:52 AM, Dave Chinner wrote: > On Sat, Feb 01, 2014 at 11:48:48AM +0800, Jeff Liu wrote: >> On 02/01 2014 00:28 AM, Mark Tinguely wrote: >>> On 01/31/14 09:51, Jeff Liu wrote: >>>> On 01/31 2014 23:30 PM, Eric Sandeen wrote: >>>>> On 1/31/14, 9:28 AM, Jeff Liu wrote: >>>>>> Well, when I looking through our bitmap source, I once thought if >>>>>> we can replace the current code with the generic bitmap library. >>>>>> However, our map is uint rather than unsigned long... >>>>> >>>>> Technically the unsigned long (pointer) is just the bitmap address, >>>>> I think. >>>> >>>> Yeah, so this might worth to try on long terms. >>> >>> The blf_data_map[] is int aligned, not long aligned. >>> You could reflect the alignment difference in the offset or >>> change the alignment in the structure. >> >> For now, I think we can not simply turn to generic bitmap just because >> of the alignment difference on 64-bits OS. > > The bitmaps end up on disk (in the log), so replacing the > implementation with a generic implementation is something we need to > be very careful about. > > IMO, we should be getting rid of the bitmaps from the > xfs_buf_log_item first (by moving to a low byte/high byte offset > range), then we only have to worry about bitmaps when doing log > recovery after a kernel upgrade on a filesystem with a dirty log. > > Getting rid of the bitmaps also solves a scalability problem with > large block sizes tracking all the changes in buffer - we burn a > huge amount of CPU walking bits when logging 64k directory buffers: > > + 21.19% [kernel] [k] xfs_dir3_leaf_check_int > + 12.20% [kernel] [k] memcpy > + 9.29% [kernel] [k] xfs_next_bit > + 5.04% [kernel] [k] xfs_buf_offset > + 3.63% [kernel] [k] xfs_buf_item_format > + 3.59% [kernel] [k] xfs_buf_item_size_segment > > The logging of xfs_buf_log_items there is consuming >30% of the CPU > being used under this workload (xfs_dir3_leaf_check_int() is high > because this is from a debug kernel.) > > IOWs, we should work to remove the bitmap code from general > operations first, then replace the remaining legacy log recovery > code with the generic bitmap implemention.... Sorry for my too late response as I was on vacations. I only moved a little progress after a quick hacking, but I can see the point in getting rid of the bitmap, just give me yet a week once I was totally return to work. Thanks, -Jeff _______________________________________________ xfs mailing list xfs@xxxxxxxxxxx http://oss.sgi.com/mailman/listinfo/xfs
