From: bugzilla@dpdk.org
To: dev@dpdk.org
Subject: [Bug 946] async flow rules affects pmd power management
Date: Wed, 02 Mar 2022 12:27:15 +0000 [thread overview]
Message-ID: <bug-946-3@http.bugs.dpdk.org/> (raw)
https://bugs.dpdk.org/show_bug.cgi?id=946
Bug ID: 946
Summary: async flow rules affects pmd power management
Product: DPDK
Version: unspecified
Hardware: All
OS: All
Status: UNCONFIRMED
Severity: normal
Priority: Normal
Component: eventdev
Assignee: dev@dpdk.org
Reporter: david.hunt@intel.com
Target Milestone: ---
pmd power management functionality when using RTM transactions never enters
power saving mode.
When testing using l3fwd-power to test the power_pmd functionality for DPDK
22.03 rc2, I noticed that the power saved in this DPDK version was
significantly reduced.
I tried multiple BIOS/OS/kernel combinations, but then I tried DPDK 21.11,
where the problem went away.
I then did a git bisect, which narrowed down the problem to commit
197e820c6685993ad75387de79707c81b5e1fc10 - "ethdev: bring in async queue-based
flow rules operations"
The patch has the effect of causing the RTM transaction in
rte_power_monitor_multi(), in the C file lib/eal/x86/rte_power_intrinsics.c, to
always fail at rte_xbegin, so we never get to the rte_power_pause, thereby we
never get to save any power.
If we revert just this patch, then the rte_xbegin succeeds, and we get to call
rte_power_pause, and save power.
So this patch is now causing rte_power_monitor_multi() to fail.
I'm not sure what the solution is, but it may be possible to re-work the async
flow rules patch, or it may be possible to re-work the pmd_power_management
code to avoid the impact of the flow rules patch. Investigation is ongoing.
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