[dpdk-dev] [PATCH v17 00/11] Add PMD power management

[Burakov, Anatoly]

On 18-Jan-21 3:24 PM, David Marchand wrote:
> On Thu, Jan 14, 2021 at 3:46 PM Anatoly Burakov
> <anatoly.burakov at intel.com> wrote:
>>
>> This patchset proposes a simple API for Ethernet drivers to cause the
>> CPU to enter a power-optimized state while waiting for packets to
>> arrive. There are multiple proposed mechanisms to achieve said power
>> savings: simple frequency scaling, idle loop, and monitoring the Rx
>> queue for incoming packages. The latter is achieved through cooperation
>> with the NIC driver that will allow us to know address of wake up event,
>> and wait for writes on that address.
>>
>> On IA, this is achieved through using UMONITOR/UMWAIT instructions. They
>> are used in their raw opcode form because there is no widespread
>> compiler support for them yet. Still, the API is made generic enough to
>> hopefully support other architectures, if they happen to implement
>> similar instructions.
>>
>> To achieve power savings, there is a very simple mechanism used: we're
>> counting empty polls, and if a certain threshold is reached, we employ
>> one of the suggested power management schemes automatically, from within
>> a Rx callback inside the PMD. Once there's traffic again, the empty poll
>> counter is reset.
>>
>> This patchset also introduces a few changes into existing power
>> management-related intrinsics, namely to provide a native way of waking
>> up a sleeping core without application being responsible for it, as well
>> as general robustness improvements. There's quite a bit of locking going
>> on, but these locks are per-thread and very little (if any) contention
>> is expected, so the performance impact shouldn't be that bad (and in any
>> case the locking happens when we're about to sleep anyway).
>>
>> Why are we putting it into ethdev as opposed to leaving this up to the
>> application? Our customers specifically requested a way to do it with
>> minimal changes to the application code. The current approach allows to
>> just flip a switch and automatically have power savings.
>>
>> Things of note:
>>
>> - Only 1:1 core to queue mapping is supported, meaning that each lcore
>>    must at most handle RX on a single queue
>> - Support 3 type policies. Monitor/Pause/Frequency Scaling
>> - Power management is enabled per-queue
>> - The API doesn't extend to other device types
>>
>> v17:
>> - Added exception for ethdev driver-only ABI
>> - Added memory barriers for monitor/wakeup (Konstantin)
>> - Fixed compiled issues on non-x86 platforms (hopefully!)
> 
> SPDK build is still broken.
> http://mails.dpdk.org/archives/test-report/2021-January/174840.html
> 
> ==== 20 line log output for Ubuntu 18.04 (dpdk_compile_spdk): ====
> rte_power_pmd_mgmt.c:(.text.experimental+0x1cc): undefined reference
> to `rte_eth_add_rx_callback'
> rte_power_pmd_mgmt.c:(.text.experimental+0x1f8): undefined reference
> to `rte_eth_get_monitor_addr'
> rte_power_pmd_mgmt.c:(.text.experimental+0x37f): undefined reference
> to `rte_eth_dev_logtype'
> /dpdk/build/lib/librte_power.a(librte_power_rte_power_pmd_mgmt.c.o):
> In function `rte_power_pmd_mgmt_queue_disable':
> rte_power_pmd_mgmt.c:(.text.experimental+0x42a): undefined reference
> to `rte_eth_dev_is_valid_port'
> rte_power_pmd_mgmt.c:(.text.experimental+0x4e7): undefined reference
> to `rte_eth_remove_rx_callback'
> rte_power_pmd_mgmt.c:(.text.experimental+0x536): undefined reference
> to `rte_eth_remove_rx_callback'
> rte_power_pmd_mgmt.c:(.text.experimental+0x54d): undefined reference
> to `rte_eth_dev_logtype'
> collect2: error: ld returned 1 exit status
> /spdk/mk/spdk.app.mk:65: recipe for target 'iscsi_fuzz' failed
> /spdk/mk/spdk.subdirs.mk:44: recipe for target 'iscsi_fuzz' failed
> /spdk/mk/spdk.subdirs.mk:44: recipe for target 'fuzz' failed
> make[4]: *** [iscsi_fuzz] Error 1
> make[3]: *** [iscsi_fuzz] Error 2
> make[2]: *** [fuzz] Error 2
> /spdk/mk/spdk.subdirs.mk:44: recipe for target 'app' failed
> make[1]: *** [app] Error 2
> /spdk/mk/spdk.subdirs.mk:44: recipe for target 'test' failed
> make: *** [test] Error 2
> [2] Error running command.
> 
> 
> I guess this is because of the added dependency of rte_ethdev to rte_power.
> Afaics, SPDK does not use pkg-config:
> https://github.com/spdk/spdk/blob/master/lib/env_dpdk/env.mk#L53
> 
> 

Sooo... this is an SPDK issue then? Because i can't see any way of 
fixing the issue on DPDK side.

-- 
Thanks,
Anatoly