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    SubjectRe: [PATCH v2 2/4] mm: vmalloc: use rwsem, mutex for vmap_area_lock and vmap_block->lock
    >     So, this patch open codes the kvmalloc() in the commit path to have
    > the above described behaviour. The result is we more than halve the
    > CPU time spend doing kvmalloc() in this path and transaction commits
    > with 64kB objects in them more than doubles. i.e. we get ~5x
    > reduction in CPU usage per costly-sized kvmalloc() invocation and
    > the profile looks like this:
    >
    > - 37.60% xlog_cil_commit
    > 16.01% memcpy_erms
    > - 8.45% __kmalloc
    > - 8.04% kmalloc_order_trace
    > - 8.03% kmalloc_order
    > - 7.93% alloc_pages
    > - 7.90% __alloc_pages
    > - 4.05% __alloc_pages_slowpath.constprop.0
    > - 2.18% get_page_from_freelist
    > - 1.77% wake_all_kswapds
    > ....
    > - __wake_up_common_lock
    > - 0.94% _raw_spin_lock_irqsave
    > - 3.72% get_page_from_freelist
    > - 2.43% _raw_spin_lock_irqsave
    > - 5.72% vmalloc
    > - 5.72% __vmalloc_node_range
    > - 4.81% __get_vm_area_node.constprop.0
    > - 3.26% alloc_vmap_area
    > - 2.52% _raw_spin_lock
    > - 1.46% _raw_spin_lock
    > 0.56% __alloc_pages_bulk
    > - 4.66% kvfree
    > - 3.25% vfree
    OK, i see. I tried to use the fs_mark in different configurations. For
    example:

    <snip>
    time fs_mark -D 10000 -S0 -n 100000 -s 0 -L 32 -d ./scratch/0 -d ./scratch/1 -d ./scratch/2 \
    -d ./scratch/3 -d ./scratch/4 -d ./scratch/5 -d ./scratch/6 -d ./scratch/7 -d ./scratch/8 \
    -d ./scratch/9 -d ./scratch/10 -d ./scratch/11 -d ./scratch/12 -d ./scratch/13 \
    -d ./scratch/14 -d ./scratch/15 -t 64 -F
    <snip>

    But i did not manage to trigger xlog_cil_commit() to fallback to vmalloc
    code. I think i should reduce an amount of memory on my kvm-pc and
    repeat the tests!

    --
    Uladzislau Rezki

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