Am Mittwoch, 16. September 2020, 15:15:55 CEST schrieb Jan Kara:
On Thu 10-09-20 07:59:13, Takashi Iwai wrote:
Do you know of a test case that fails using PREEMPT
VOLUNTARY vs. NONE or where it's seen that one performs significantly better under some workload? How typical is the workload?
Note: PREEMPT NONE is for kernels used for scientific computation
that needs the raw processing power of the kernel, regardless of scheduling latencies. I'm not doing such work straight computing, but instead use the server, mostly, for serving incoming network requests. Depending on packet and request size, One(1) 10Gb connection can saturate a single cpu.
Supposedly RedHat disabled various C-States if you use 9K network packets, as long latencies imposed by deeper power saving states can theoretically cause some packet loss. If the cpu is not preemptable, wouldn't the same situation exist? Conversely I see some disable Jumbo packets, which, when compared to standard, causes network throughput drop from 400-600MB/s down to 110MB/s. That's unacceptable for servers serving internal network requests.
How much does 'Preempt none' benefit what workload over voluntary?
This can be answered best by the performance team, who has been carrying the tests and evaluations.
I believe Mel did some comparisons for this in the past. Mel?
As noted in the other leg of this thread, apart from PREEMPT_NONE, the NO_HZ_FULL vs. NO_HZ_IDLE should be included into this discussion. Pete -- To unsubscribe, e-mail: opensuse+unsubscribe@opensuse.org To contact the owner, e-mail: opensuse+owner@opensuse.org