Messages in this thread | | | Date | Wed, 13 Mar 2024 18:06:24 -0400 | Subject | Re: [RFC PATCH 0/2] Introduce serialized smp_call_function APIs | From | Mathieu Desnoyers <> |
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On 2024-03-13 17:14, Avi Kivity wrote: > On Wed, 2024-03-13 at 16:56 -0400, Mathieu Desnoyers wrote: >> commit 944d5fe50f3f ("sched/membarrier: reduce the ability to hammer >> on sys_membarrier") >> introduces a mutex over all membarrier operations to reduce its ability >> to slow down the rest of the system. >> >> This RFC series has two objectives: >> >> 1) Move this mutex to the smp_call_function APIs so other system calls >> using smp_call_function IPIs are limited in the same way, >> >> 2) Restore scalability of MEMBARRIER_CMD_PRIVATE_EXPEDITED_RSEQ with >> MEMBARRIER_CMD_FLAG_CPU, which targets specific CPUs with IPIs. >> This may or may not be useful, and I would welcome benchmarks from >> users of this feature to figure out if this is worth it. >> >> This series applies on top of v6.8. >> > > > I see this doesn't restore scaling of MEMBARRIER_CMD_PRIVATE_EXPEDITED, > which I use (and wasn't aware was broken).
It's mainly a mitigation for IPI Storming: CVE-2024-26602 disclosed as part of [1].
> > I don't have comments on the patches, but do have ideas on how to work > around the problem in Seastar. So this was a useful heads-up for me.
Note that if you don't use membarrier private expedited too heavily, you should not notice any difference. But nevertheless I would be interested to hear about any regression on performance of real workloads resulting from commit 944d5fe50f3f.
Thanks,
Mathieu
[1] https://www.vusec.net/projects/ghostrace/
-- Mathieu Desnoyers EfficiOS Inc. https://www.efficios.com
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