On 03/21/2011 06:54 PM, Eric Dumazet wrote:
Le lundi 21 mars 2011 Ã 22:01 +0545, Ben Nagy a Ãcrit : > >> On Mon, Mar 21, 2011 at 7:38 PM, Avi Kivity<avi@xxxxxxxxxx> wrote: > >> > In the future, please post the binary perf.dat. > >> > >> Hi Avi, > >> > >> How do I do that? > > > > 'make nconfig' and go to the kernel hacking section. > > Imprecise question sorry, I meant how do I get the perf.dat not how do > I disable the debugging. > > On the non-debug kernel: Linux eax 2.6.38-7-server #36-Ubuntu SMP Fri > Mar 18 23:36:13 UTC 2011 x86_64 x86_64 x86_64 GNU/Linux > > 150512.00 67.8% __ticket_spin_lock > [kernel.kallsyms] > 11126.00 5.0% memcmp_pages > [kernel.kallsyms] > 9563.00 4.3% native_safe_halt > [kernel.kallsyms] > 8965.00 4.0% svm_vcpu_run > /lib/modules/2.6.38-7-server/kernel/arch/x86/kvm/kvm-amd.ko > 6489.00 2.9% tg_load_down > [kernel.kallsyms] > 4676.00 2.1% kvm_get_cs_db_l_bits > /lib/modules/2.6.38-7-server/kernel/arch/x86/kvm/kvm.ko > 1931.00 0.9% load_balance_fair > [kernel.kallsyms] > 1917.00 0.9% ktime_get > [kernel.kallsyms] > 1624.00 0.7% walk_tg_tree.clone.129 > [kernel.kallsyms] > 1542.00 0.7% find_busiest_group > [kernel.kallsyms] > 1326.00 0.6% find_next_bit > [kernel.kallsyms] > 673.00 0.3% lock_hrtimer_base.clone.25 > [kernel.kallsyms] > 624.00 0.3% copy_user_generic_string [kernel.kallsyms] > > top now says: > > top - 00:11:35 up 22 min, 4 users, load average: 0.11, 6.15, 7.78 > Tasks: 491 total, 3 running, 488 sleeping, 0 stopped, 0 zombie > Cpu(s): 0.9%us, 15.4%sy, 0.0%ni, 83.7%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st > Mem: 99068660k total, 70831760k used, 28236900k free, 10036k buffers > Swap: 2438140k total, 2173652k used, 264488k free, 3396144k cached > > With average 'resting cpu' per idle guest 8%, 96 guests running. > > Is this as good as I am going to get? It seems like I can't really > debug that lock contention without blowing stuff up because of the > load of the lock debugging... > > Don't know if I mentioned this before, but those guests are each > pinned to a cpu (cpu guestnum%48) with taskset. > > Cheers, It seems you hit idr_lock contention (used in kernel/posix-timers.c)
Any ideas on how to fix it? We could pre-allocate IDs and batch them in per-cpu caches, but it seems like a lot of work.
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