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authorIngo Molnar <mingo@kernel.org>2014-08-22 08:04:15 (GMT)
committerIngo Molnar <mingo@kernel.org>2014-08-22 08:04:15 (GMT)
commit80b304fd00e8b667775ff791121b61ecd7cd0c03 (patch)
treeb4f2ec59fe062c43343ee4c2f10a6bcd0e4dcd1b /Documentation/networking/pktgen.txt
parentfb21b84e7f809ef04b1e5aed5d463cf0d4866638 (diff)
parent6a7519e81321343165f89abb8b616df186d3e57a (diff)
downloadlinux-80b304fd00e8b667775ff791121b61ecd7cd0c03.tar.xz
Merge tag 'efi-urgent' of git://git.kernel.org/pub/scm/linux/kernel/git/mfleming/efi into x86/urgent
Pull EFI fixes from Matt Fleming: * WARN_ON(!spin_is_locked()) always triggers on non-SMP machines. Swap it for the more canonical lockdep_assert_held() which always does the right thing - Guenter Roeck * Assign the correct value to efi.runtime_version on arm64 so that all the runtime services can be invoked - Semen Protsenko Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'Documentation/networking/pktgen.txt')
-rw-r--r--Documentation/networking/pktgen.txt28
1 files changed, 28 insertions, 0 deletions
diff --git a/Documentation/networking/pktgen.txt b/Documentation/networking/pktgen.txt
index 0e30c78..0dffc6e 100644
--- a/Documentation/networking/pktgen.txt
+++ b/Documentation/networking/pktgen.txt
@@ -24,6 +24,34 @@ For monitoring and control pktgen creates:
/proc/net/pktgen/ethX
+Tuning NIC for max performance
+==============================
+
+The default NIC setting are (likely) not tuned for pktgen's artificial
+overload type of benchmarking, as this could hurt the normal use-case.
+
+Specifically increasing the TX ring buffer in the NIC:
+ # ethtool -G ethX tx 1024
+
+A larger TX ring can improve pktgen's performance, while it can hurt
+in the general case, 1) because the TX ring buffer might get larger
+than the CPUs L1/L2 cache, 2) because it allow more queueing in the
+NIC HW layer (which is bad for bufferbloat).
+
+One should be careful to conclude, that packets/descriptors in the HW
+TX ring cause delay. Drivers usually delay cleaning up the
+ring-buffers (for various performance reasons), thus packets stalling
+the TX ring, might just be waiting for cleanup.
+
+This cleanup issues is specifically the case, for the driver ixgbe
+(Intel 82599 chip). This driver (ixgbe) combine TX+RX ring cleanups,
+and the cleanup interval is affected by the ethtool --coalesce setting
+of parameter "rx-usecs".
+
+For ixgbe use e.g "30" resulting in approx 33K interrupts/sec (1/30*10^6):
+ # ethtool -C ethX rx-usecs 30
+
+
Viewing threads
===============
/proc/net/pktgen/kpktgend_0