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SubjectRe: 2.1.114 VFS code 5x slower than 2.0.33?!?
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Andi Kleen <ak@muc.de> writes:

[hate to follow myself up, but ...]

> I repeated your tests with kernel profiling on 2.1.114:
>
> Creation:
> 28.42user 59.63system 2:18.66elapsed 63%CPU (0avgtext+0avgdata 0maxresident)k
> 0inputs+0outputs (710242major+390114minor)pagefaults 0swaps
>
> ...
> 64 1.05% c011ab7c zap_page_range
> 68 1.11% c011a9b4 copy_page_range
> 81 1.33% c01383e0 ext2_get_group_desc
> 95 1.56% c0126134 get_hash_table
> 98 1.61% c010ada0 show_registers (this appears often in
> other kernel profiles too - anyone know the reason?)
> 111 1.82% c013a994 ext2_new_inode
> 192 3.16% c011d988 filemap_nopage
> 382 6.28% c01396c0 ext2_readdir
> 463 7.62% c011b384 do_wp_page
> 823 13.54% c013c6e0 ext2_find_entry
> 953 15.68% c013ca38 ext2_add_entry
> 1263 20.79% c013960c ext2_check_dir_entry
^^^^^^^^^^^^^^^^^^^^^^
This is bogus. ext2_check_dir_entry is just a small function that does
some check - it should never take up that much run time. Anyone have any
theories on this? Or is my profile hosed, can anyone else reproduce it?

I instrumented my kernel and in about 3h of moderate X11 usage it called
ext2_check_dir_entry 1520890 times, which seems a bit high.

-Andi

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