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    SubjectRe: [PATCH 0/7] breaking the global file_list_lock
    Ingo Molnar wrote:
    > * Christoph Hellwig <hch@infradead.org> wrote:
    >
    >> On Sun, Jan 28, 2007 at 12:51:18PM +0100, Peter Zijlstra wrote:
    >>> This patch-set breaks up the global file_list_lock which was found
    >>> to be a severe contention point under basically any filesystem
    >>> intensive workload.
    >> Benchmarks, please. Where exactly do you see contention for this?
    >
    > it's the most contended spinlock we have during a parallel kernel
    > compile on an 8-way system. But it's pretty common-sense as well,
    > without doing any measurements, it's basically the only global lock left
    > in just about every VFS workload that doesnt involve massive amount of
    > dentries created/removed (which is still dominated by the dcache_lock).
    >
    >> filesystem intensive workload apparently means namespace operation
    >> heavy workload, right? The biggest bottleneck I've seen with those is
    >> dcache lock.
    >
    > the dcache lock is not a problem during kernel compiles. (its
    > rcu-ification works nicely in that workload)

    Mmm. not wholly convinced that's true. Whilst i don't have lockmeter
    stats to hand, the heavy time in __d_lookup seems to indicate we may
    still have a problem to me. I guess we could move the spinlocks out
    of line again to test this fairly easily (or get lockmeter upstream).

    114076 total 0.0545
    57766 default_idle 916.9206
    11869 prep_new_page 49.4542
    3830 find_trylock_page 67.1930
    2637 zap_pte_range 3.9125
    2486 strnlen_user 54.0435
    2018 do_page_fault 1.1941
    1940 do_wp_page 1.6973
    1869 __d_lookup 7.7231
    1331 page_remove_rmap 5.2196
    1287 do_no_page 1.6108
    1272 buffered_rmqueue 4.6423
    1160 __copy_to_user_ll 14.6835
    1027 _atomic_dec_and_lock 11.1630
    655 release_pages 1.9670
    644 do_path_lookup 1.6304
    630 schedule 0.4046
    617 kunmap_atomic 7.7125
    573 __handle_mm_fault 0.7365
    548 free_hot_page 78.2857
    500 __copy_user_intel 3.3784
    483 copy_pte_range 0.5941
    482 page_address 2.9571
    478 file_move 9.1923
    441 do_anonymous_page 0.7424
    429 filemap_nopage 0.4450
    401 anon_vma_unlink 4.8902
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