While testing zram I ran a script that creates a block devices,
creates a filesystem on in and untars Qt on that filesystem.
I was surprised to find ext4_mb_scan_aligned near the top of the profile output.
This was evidently because the command "mke2fs -t ext4 -m 0 -I 128 -O
^has_journal,^ext_attr <block device>"
created a filesystem with (output of tune2fs):
RAID stride: 1
RAID stripe width: 1
I thought this strange and removed these values using debugfs:
set_super_value raid_stride 0
set_super_value raid_stripe_width 0
With this "fix" the symbol ext4_mb_scan_aligned disappeared from perf's output:
18.98% -3.66% gzip [.] zip
0.00% +14.84% [kernel.kallsyms] [k] ext4_mb_scan_aligned
17.91% -3.44% gzip [.]
treat_file.part.4.2264
13.73% -2.47% [csnappy_compress] [k]
snappy_compress_fragment
3.96% -0.77% [kernel.kallsyms] [k]
copy_user_generic_string
3.05% -0.41% libc-2.13.so [.] __memcpy_ssse3
0.89% +1.49% [kernel.kallsyms] [k] _raw_spin_lock
2.63% -0.49% [kernel.kallsyms] [k] __memcpy
1.61% -0.17% [kernel.kallsyms] [k] __memset
0.78% -0.11% [kernel.kallsyms] [k] ext4_mark_iloc_dirty
0.63% -0.11% [kernel.kallsyms] [k] system_call
0.66% -0.14% gzip [.] treat_stdin.2262
0.58% -0.12% libc-2.13.so [.] _int_malloc
This is using mke2fs 1.41.14 (22-Dec-2010) on Linux 2.6.38.2.
Is this expected behavior? Do you need me to provide more information?
regards,
-Z.T.
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