netdev - RE: Low performance Intel 10GE NIC (3.2.10) on 2.6.38 Kernel

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Date:	Fri, 8 Apr 2011 20:19:41 +0800
From:	Wei Gu <wei.gu@...csson.com>
To:	Eric Dumazet <eric.dumazet@...il.com>,
	Alexander Duyck <alexander.h.duyck@...el.com>
CC:	netdev <netdev@...r.kernel.org>,
	"Kirsher, Jeffrey T" <jeffrey.t.kirsher@...el.com>
Subject: RE: Low performance Intel 10GE NIC (3.2.10) on 2.6.38 Kernel

Hi again,
I tried more testing with by disable this CONFIG_DMAR with shipped 2.6.38 ixgbe and Intel released 3.2.10/3.1.15.
All these test looks we can get >1Mpps 400bype packtes but not stable at all, there will huge number missing errors with 100% CPU IDLE:
ethtool -S eth10 |grep rx_missed_errors

        rx_missed_errors: 76832040

SUM: 1102212 ETH8: 0  ETH10: 1102212 ETH6: 0 ETH4: 0
SUM: 521841 ETH8: 0  ETH10: 521841 ETH6: 0 ETH4: 0
SUM: 426776 ETH8: 0  ETH10: 426776 ETH6: 0 ETH4: 0
SUM: 927520 ETH8: 0  ETH10: 927520 ETH6: 0 ETH4: 0
SUM: 1171995 ETH8: 0  ETH10: 1171995 ETH6: 0 ETH4: 0
SUM: 855980 ETH8: 0  ETH10: 855980 ETH6: 0 ETH4: 0


Do you know if there is other options in the kernel will cause high rate rx_missed_errors with low CPU usage. (No problem on 2.6.32 with same test case)

perf  record:
+     69.74%          swapper  [kernel.kallsyms]          [k] poll_idle
+     11.62%          swapper  [kernel.kallsyms]          [k] intel_idle
+      0.80%          swapper  [ixgbe]                    [k] ixgbe_poll
+      0.79%             perf  [ixgbe]                    [k] ixgbe_poll
+      0.77%             perf  [kernel.kallsyms]          [k] skb_copy_bits
+      0.64%          swapper  [kernel.kallsyms]          [k] skb_copy_bits
+      0.48%             perf  [kernel.kallsyms]          [k] __kmalloc_node_track_caller
+      0.44%          swapper  [kernel.kallsyms]          [k] __kmalloc_node_track_caller
+      0.36%          swapper  [kernel.kallsyms]          [k] kmem_cache_alloc_node
+      0.35%          swapper  [kernel.kallsyms]          [k] kfree
+      0.35%             perf  [kernel.kallsyms]          [k] kmem_cache_alloc_node


-----Original Message-----
From: Eric Dumazet [mailto:eric.dumazet@...il.com]
Sent: Friday, April 08, 2011 5:08 PM
To: Wei Gu
Cc: Alexander Duyck; netdev; Kirsher, Jeffrey T
Subject: RE: Low performance Intel 10GE NIC (3.2.10) on 2.6.38 Kernel

Le vendredi 08 avril 2011 à 16:59 +0800, Wei Gu a écrit :
> Hi,
> On my configuration of Linux 2.6.38 we do enabled the CONFIG_DMAR
> CONFIG_DMAR=y CONFIG_DMAR_DEFAULT_ON=y CONFIG_DMAR_FLOPPY_WA=y
> CONFIG_INTR_REMAP=y
>
> But I enabled this DMAR also by default of the RHEL6 2.6.32 kernel,
> which we don't see this problem on this kernel. The only different I
> can see on the config is "CONFIG_DMAR_DEFAULT_ON"
> CONFIG_DMAR=y
> # CONFIG_DMAR_DEFAULT_ON is not set
> CONFIG_DMAR_FLOPPY_WA=y
> CONFIG_INTR_REMAP=y
>
> I could try the same configuration as 2.6.32 for the 2.6.38 kernel by
> unset the CONFIG_DMAR_DEFAULT_ON. And run the test again, hopefully we
> can get the test result next Monday:)

Just say no to CONFIG_DMAR, end of problems, no need to try various knobs and find the solution next month ;)

Unless you have a reason to use it.



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