From: bugzilla@dpdk.org
To: dev@dpdk.org
Subject: [Bug 1231] l3fwd: perf reports affected by silently enabling "fast free"
Date: Tue, 16 May 2023 08:37:03 +0000 [thread overview]
Message-ID: <bug-1231-3@http.bugs.dpdk.org/> (raw)
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https://bugs.dpdk.org/show_bug.cgi?id=1231
Bug ID: 1231
Summary: l3fwd: perf reports affected by silently enabling
"fast free"
Product: DPDK
Version: unspecified
Hardware: All
OS: All
Status: UNCONFIRMED
Severity: normal
Priority: Normal
Component: examples
Assignee: dev@dpdk.org
Reporter: mb@smartsharesystems.com
Target Milestone: ---
The l3fwd example application is used for benchmarking, including the official
NIC performance reports published on the DPDK web site [1].
A patch to silently enable the "fast free" (RTE_ETH_TX_OFFLOAD_MBUF_FAST_FREE)
optimization was applied to l3fwd [2][3] in January 2018.
This means that the performance reports starting from DPDK 18.02 do not reflect
generic performance, but the performance of applications that meet the
preconditions for using this optimization feature.
In order to prevent misleading performance results, such non-generic
optimizations should be not be silently enabled; they should be explicitly
enabled using a command line option in l3fwd.
The same applies to the coming "buffer recycle" optimization.
[1]: https://core.dpdk.org/perf-reports/
[2]: http://inbox.dpdk.org/dev/cover.1514280003.git.shahafs@mellanox.com/
[3]:
http://git.dpdk.org/dpdk/commit/examples/l3fwd/main.c?id=1ef9600b2d20078538ca4082f9a4adf2d9bd2ab2
PS: I don't oppose to NIC vendors publishing performance results using
non-generic optimizations such as "fast free" or the coming "buffer recycle",
but it should be fully disclosed which optimizations have been used to achieve
better results.
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