Bug 1147 - ENA NET PMD tracing function enabled on transmit fastpath in non-debug builds
Summary: ENA NET PMD tracing function enabled on transmit fastpath in non-debug builds
Status: UNCONFIRMED
Alias: None
Product: DPDK
Classification: Unclassified
Component: ethdev (show other bugs)
Version: 21.08
Hardware: All Linux
: Normal major
Target Milestone: ---
Assignee: dev
URL:
Depends on:
Blocks:
 
Reported: 2022-12-12 11:14 CET by Declan Doherty
Modified: 2023-08-20 13:31 CEST (History)
1 user (show)



Attachments
Flamegraph of testpmd and ena pmd on AWS (66.94 KB, image/png)
2022-12-12 11:14 CET, Declan Doherty
Details

Description Declan Doherty 2022-12-12 11:14:17 CET
Created attachment 237 [details]
Flamegraph of testpmd and ena pmd on AWS

During performance benchmarking on AWS with VPP, a significant cycle count increase was noticed within the ENA PMD transmit burst. 

Further investigation with testpmd shows the same cycle count increase, which is in the order of 10 X compared to pre 21.08 release.

The issues seems to relate to in changes in commit 0a001d69bca086c5a6e62b10552192380efee1f0, which changes the default behaviour of the  ena_trc_** macros, some of which are on the fast path, to always invoke rte_log. 

See attach flame graph, for testpmd in mac forward mode, where a huge percentage of time is spent checking whether to log the trace.

Issue seems to effect all version of DPDK from 21.08 forwards.
Comment 1 shaibran 2023-08-20 13:31:22 CEST
I will review the ena macro to check if there is a need to separate the macro for fastpath to avoid the time consuming check

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