Messages in this thread | | | Date | Fri, 16 Jun 2023 22:14:52 +0200 | Subject | Re: [PATCH 0/5] x86/speculation: Disable IBRS when idle | From | "Robin Jarry" <> |
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Waiman Long, Jun 16, 2023 at 21:59: > For Intel processors that need to turn on IBRS to protect against > Spectre v2 and Retbleed, the IBRS bit in the SPEC_CTRL MSR affects > the performance of the whole core even if only one thread is turning > it on when running in the kernel. For user space heavy applications, > the performance impact of occasionally turning IBRS on during syscalls > shouldn't be significant. Unfortunately, that is not the case when the > sibling thread is idling in the kernel. In that case, the performance > impact can be significant. > > When DPDK is running on an isolated CPU thread processing network packets > in user space while its sibling thread is idle. The performance of the > busy DPDK thread with IBRS on and off in the sibling idle thread are: > > IBRS on IBRS off > ------- -------- > packets/second: 7.8M 10.4M > avg tsc cycles/packet: 282.26 209.86 > > This is a 25% performance degradation. The test system is a Intel Xeon > 4114 CPU @ 2.20GHz. > > This patch series turns off IBRS when in various idle mode to eliminate > the performance impact of the idling thread on its busy sibling thread.
Hi Longman,
thanks a lot for the quick turnaround on this issue.
Tested-by: Robin Jarry <rjarry@redhat.com>
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