From: Fiona Trahe Date: Tue, 7 Feb 2017 16:32:55 +0000 (+0000) Subject: doc: add limitations section to cryptoperf guide X-Git-Tag: spdx-start~4509 X-Git-Url: http://git.droids-corp.org/?a=commitdiff_plain;h=4fa706bf48a1779f4f3cd917864c44f14bda39f4;p=dpdk.git doc: add limitations section to cryptoperf guide Add limitations to use of the dpdk-test-crypto-perf tool for hardware accelerator measurements Signed-off-by: Fiona Trahe Acked-by: Slawomir Mrozowicz --- diff --git a/doc/guides/tools/cryptoperf.rst b/doc/guides/tools/cryptoperf.rst index 6832312d6a..1fc40c4447 100644 --- a/doc/guides/tools/cryptoperf.rst +++ b/doc/guides/tools/cryptoperf.rst @@ -41,6 +41,21 @@ chain mode have to be specified in the command line as application parameters. These parameters are checked using device capabilities structure. +Limitations +----------- +On hardware devices the cycle-count doesn't always represent the actual offload +cost. The cycle-count only represents the offload cost when the hardware +accelerator is not fully loaded, when loaded the cpu cycles freed up by the +offload are still consumed by the test tool and included in the cycle-count. +These cycles are consumed by retries and inefficient API calls enqueuing and +dequeuing smaller bursts than specified by the cmdline parameter. This results +in a larger cycle-count measurement and should not be interpreted as an offload +cost measurement. + +On hardware devices the throughput measurement is not necessarily the maximum +possible for the device, e.g. it may be necessary to use multiple cores to keep +the hardware accelerator fully loaded and so measure maximum throughput. + Compiling the Application -------------------------