[RFC] new jbd locking

From: Alex Tomas (bzzz@tmi.comex.ru)
Date: Sun May 18 2003 - 11:54:19 EST


hi!

here is new version of the patch. following problems have been fixed
since last one:
- bug in log_do_checkpoint(): some buffer were locked,
  but I/O didn't get started (thanks to Dave Hansen for testing)
- minor memory leak has been fixed
- now b_committed_data is protected from to be freed
  by journal_commit_transaction()

some benchmarks:

1) dbench
   I have a lot of troubles with dbench because results are very
   unstable and unpredictable. so, I collected results of several
   runs and calculated average thoughput. unfortunately, even average
   numbers are unstable

   dbench 1: before after
                73.63975 70.20113
                71.55381 72.89969
                69.54363 70.46640
                72.24077 69.91244

   dbench 2: before after
                95.92940 100.22570
                86.85545 90.09191
                90.98304 105.07921
                84.86959 85.68771

   dbench 4: before after
                45.64170 53.43416
                48.66928 57.15186
                49.71130 56.51542

   dbench 16: before after
                41.13922 52.74798
                50.43494 51.12468
                42.23480 54.16548
                44.76376 53.92670

2) synthetic test

    N (1/2/4) processes write 32 blocks into own file, then truncate file to zero
    and repeat this sequence for 100000 times:

             4/32/100000 2/32/100000 1/32/100000
    before: 11m13.389s 4m48.604s 1m51.323s
    after: 5m38.025s 2m47.733s 1m56.503s

all tests were performed on dual p3-1GHz/512MB/old scsi hdd

you should apply two patches (against 2.5.69-mm6):
1) new locking schema for jbd
2) patch that makes ext3 allocation safe with new locking schema

I'll be happy to see any comments

with best regards, Alex





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