2009/6/18 Markus Trippelsdorf <markus@trippelsdorf.de>:
quoted text
> I'm running the latest git kernel and git btrfs-progs.
> When I try to run some benchmarks on my btrfs partition I always get
> read errors:
>
> phenom2 ~ # iozone -I -a -s 100M -r 4k -i 0 -i 1 -i 2
>        Iozone: Performance Test of File I/O
>                Version $Revision: 3.321 $
>                Compiled for 64 bit mode.
>                Build: linux-AMD64
>
>        Contributors:William Norcott, Don Capps, Isom Crawford, Kirby Collins
>                     Al Slater, Scott Rhine, Mike Wisner, Ken Goss
>                     Steve Landherr, Brad Smith, Mark Kelly, Dr. Alain CYR,
>                     Randy Dunlap, Mark Montague, Dan Million, Gavin Brebner,
>                     Jean-Marc Zucconi, Jeff Blomberg, Benny Halevy,
>                     Erik Habbinga, Kris Strecker, Walter Wong, Joshua Root.
>
>        Run began: Thu Jun 18 10:18:06 2009
>
>        O_DIRECT feature enabled
>        Auto Mode
>        File size set to 102400 KB
>        Record Size 4 KB
>        Command line used: iozone -I -a -s 100M -r 4k -i 0 -i 1 -i 2
>        Output is in Kbytes/sec
>        Time Resolution = 0.000001 seconds.
>        Processor cache size set to 1024 Kbytes.
>        Processor cache line size set to 32 bytes.
>        File stride size set to 17 * record size.
>                                                            random  random    bkwd   record   stride
>              KB  reclen   write rewrite    read    reread    read   write    read  rewrite     read   fwrite frewrite   fread  freread
>          102400       4    7540    5981
> Error reading block 0 ef000000
> read: Invalid argument
>
> phenom2 /tmp # sysbench  --file-extra-flags=direct  --num-threads=16 --test=fileio --file-total-size=100M --file-test-mode=rndrd prepare             sysbench 0.4.10:  multi-threaded system evaluation benchmark
>
> 128 files, 800Kb each, 100Mb total
> Creating files for the test...
> phenom2 /tmp # sysbench  --file-extra-flags=direct  --num-threads=16 --test=fileio --file-total-size=100M --file-test-mode=rndrd run
> sysbench 0.4.10:  multi-threaded system evaluation benchmark
>
> Running the test with following options:
> Number of threads: 16
>
> Extra file open flags: 16384
> 128 files, 800Kb each
> 100Mb total file size
> Block size 16Kb
> Number of random requests for random IO: 10000
> Read/Write ratio for combined random IO test: 1.50
> Periodic FSYNC enabled, calling fsync() each 100 requests.
> Calling fsync() at the end of test, Enabled.
> Using synchronous I/O mode
> Doing random read test
> Threads started!
> FATAL: Failed to read file! file: 3 pos: 196608 errno = 22 ()
> FATAL: Failed to read file! file: 13 pos: 524288 errno = 22 ()
> FATAL: Failed to read file! file: 48 pos: 180224 errno = 22 ()
> FATAL: Failed to read file! file: 96 pos: 262144 errno = 22 ()
> FATAL: Failed to read file! file: 26 pos: 311296 errno = 22 ()
> FATAL: Failed to read file! file: 26 pos: 507904 errno = 22 ()
> FATAL: Failed to read file! file: 127 pos: 589824 errno = 22 ()
> FATAL: Failed to read file! file: 3 pos: 0 errno = 22 ()
> FATAL: Failed to read file! file: 119 pos: 262144 errno = 22 ()
> FATAL: Failed to read file! file: 9 pos: 688128 errno = 22 ()
> FATAL: Failed to read file! file: 62 pos: 557056 errno = 22 ()
> FATAL: Failed to read file! file: 87 pos: 655360 errno = 22 ()
> FATAL: Failed to read file! file: 113 pos: 425984 errno = 22 ()
> FATAL: Failed to read file! file: 20 pos: 344064 errno = 22 ()
> FATAL: Failed to read file! file: 17 pos: 294912 errno = 22 ()
> FATAL: Failed to read file! file: 16 pos: 0 errno = 22 ()
> Done.
>

Currently, btrfs doesn't support using direct I/O for read.

Yan
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