On Tue, 2007-06-19 at 07:25 -0700, Vernon Mauery wrote: > On Monday 18 June 2007 11:51:38 pm Peter Zijlstra wrote: > > On Mon, 2007-06-18 at 22:12 -0700, Vernon Mauery wrote: > > > In looking at the performance characteristics of my network I found that > > > 2.6.21.5-rt15 suffers from degraded thoughput with multiple threads. The > > > test that I did this with is simply invoking 1, 2, 4, and 8 instances of > > > netperf at a time and measuring the total throughput. I have two 4-way > > > machines connected with 10GbE cards. I tested several kernels (some > > > older and some newer) and found that the only thing in common was that > > > with -RT kernels the performance went down with concurrent streams. > > > > > > While the test was showing the numbers for receiving as well as sending, > > > the receiving numbers are not reliable because that machine was running a > > > -RT kernel for these tests. > > > > > > I was just wondering if anyone had seen this problem before or would have > > > any idea on where to start hunting for the solution. > > > > could you enable CONFIG_LOCK_STAT > > > > echo 0 > /proc/lock_stat > > > > <run your test> > > > > and report the output of (preferably not 80 column wrapped): > > > > grep : /proc/lock_stat | head > > /proc/lock_stat stayed empty for the duration of the test. I am guessing > this > means there was no lock contention.
Most likely caused by the issue below. > I do see this on the console: > BUG: scheduling with irqs disabled: IRQ-8414/0x00000000/9494 > caller is wait_for_completion+0x85/0xc4 > > Call Trace: > [<ffffffff8106f3b2>] dump_trace+0xaa/0x32a > [<ffffffff8106f673>] show_trace+0x41/0x64 > [<ffffffff8106f6ab>] dump_stack+0x15/0x17 > [<ffffffff8106566f>] schedule+0x82/0x102 > [<ffffffff81065774>] wait_for_completion+0x85/0xc4 > [<ffffffff81092043>] set_cpus_allowed+0xa1/0xc8 > [<ffffffff810986e2>] do_softirq_from_hardirq+0x105/0x12d > [<ffffffff810ca6cc>] do_irqd+0x2a8/0x32f > [<ffffffff8103469d>] kthread+0xf5/0x128 > [<ffffffff81060f68>] child_rip+0xa/0x12 > > INFO: lockdep is turned off. > > I haven't seen this until I enabled lock_stat and ran the test. I think this is what causes the lack of output. It disables all lock tracking features... > > or otherwise if there are any highly contended network locks listed? > > Any other ideas for debugging this? fixing the above bug would help :-) Ingo says that should be fixed in -rt17, so if you could give that a spin... - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
