On 16 December 2021 19:55:36 GMT, Tom Lendacky <thomas.lendacky@xxxxxxx> wrote: >On 12/16/21 1:52 PM, David Woodhouse wrote: >> On Thu, 2021-12-16 at 10:27 -0600, Tom Lendacky wrote: >>> On 12/15/21 8:56 AM, David Woodhouse wrote: >>> >>>> Doing the INIT/SIPI/SIPI in parallel for all APs and *then* waiting for >>>> them shaves about 80% off the AP bringup time on a 96-thread socket >>>> Skylake box (EC2 c5.metal) — from about 500ms to 100ms. >>>> >>>> There are more wins to be had with further parallelisation, but this is >>>> the simple part. >>> >>> I applied this series and began booting a regular non-SEV guest and hit a >>> failure at 39 vCPUs. No panic or warning, just a reset and OVMF was >>> executing again. I'll try to debug what's going, but not sure how quickly >>> I'll arrive at anything. >> >> I've pushed the SEV-ES fix to >> https://git.infradead.org/users/dwmw2/linux.git/shortlog/refs/heads/parallel-5.16 >> and in doing so I've moved the 'no_parallel_bringup' command line >> argument earlier in the series, to Thomas's "Support parallel startup >> of secondary CPUs" commit (now 191f0899757). It would be interesting to >> see if you can reproduce with just that much, both with and with >> no_parallel_bringup. And then whether the subsequent commit that >> actually enables the parallel INIT/SIPI/SIPI actually makes the >> difference? >> > >I'll pull it down and give it try. Thanks. Note: don't use the whole thing; that last "parallel part2" patch in particular isn't ready. And probably isn't where the next low-hanging fruit is anyway. -- Sent from my Android device with K-9 Mail. Please excuse my brevity.
