Alexander Motin wrote:
> Hi.
>
> While profiling netgraph operation on UP HEAD router I have found that
> huge amount of time it spent on memory allocation/deallocation:
>
> 0.14 0.05 132119/545292 ip_forward <cycle 1> [12]
> 0.14 0.05 133127/545292 fxp_add_rfabuf [18]
> 0.27 0.10 266236/545292 ng_package_data [17]
> [9]14.1 0.56 0.21 545292 uma_zalloc_arg [9]
> 0.17 0.00 545292/1733401 critical_exit <cycle 2> [98]
> 0.01 0.00 275941/679675 generic_bzero [68]
> 0.01 0.00 133127/133127 mb_ctor_pack [103]
>
> 0.15 0.06 133100/545266 mb_free_ext [22]
> 0.15 0.06 133121/545266 m_freem [15]
> 0.29 0.11 266236/545266 ng_free_item [16]
> [8]15.2 0.60 0.23 545266 uma_zfree_arg [8]
> 0.17 0.00 545266/1733401 critical_exit <cycle 2> [98]
> 0.00 0.04 133100/133100 mb_dtor_pack [57]
> 0.00 0.00 134121/134121 mb_dtor_mbuf [111]
>
> I have already optimized all possible allocation calls and those that
> left are practically unavoidable. But even after this kgmon tells that
> 30% of CPU time consumed by memory management.
>
> So I have some questions:
> 1) Is it real situation or just profiler mistake?
> 2) If it is real then why UMA is so slow? I have tried to replace it in
> some places with preallocated TAILQ of required memory blocks protected
> by mutex and according to profiler I have got _much_ better results.
> Will it be a good practice to replace relatively small UMA zones with
> preallocated queue to avoid part of UMA calls?
> 3) I have seen that UMA does some kind of CPU cache affinity, but does
> it cost so much that it costs 30% CPU time on UP router?
given this information, I would add an 'item cache' in ng_base.c
(hmm do I already have one?)
>
> Thanks!
>
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