On Wed, 2023-02-01 at 20:43 +0000, Usama Arif wrote: > This patchseries is from the work done by David Woodhouse (v4: https://lore.kernel.org/all/20220201205328.123066-1-dwmw2@xxxxxxxxxxxxx/). > The parallel CPU bringup is disabled for all AMD CPUs in this version: (see discussions: https://lore.kernel.org/all/bc3f2b1332c4bb77558df8aa36493a55542fe5b9.camel@xxxxxxxxxxxxx/ and > https://lore.kernel.org/all/3b6ac86fdc800cac5806433daf14a9095be101e9.camel@xxxxxxxxxxxxx/). > > Doing INIT/SIPI/SIPI in parallel brings down the time for smpboot from ~700ms > to 100ms (85% improvement) on a server with 128 CPUs split across 2 NUMA > nodes. > > Adding another cpuhp state for do_wait_cpu_initialized to make sure cpu_init > is reached in parallel as proposed by David in v1 will bring it down further > to ~30ms. Making this change would be dependent on this patchseries, so they > could be explored if this gets merged. > > Changes across versions: > v2: Cut it back to just INIT/SIPI/SIPI in parallel for now, nothing more > v3: Clean up x2apic patch, add MTRR optimisation, lock topology update > in preparation for more parallelisation. > v4: Fixes to the real mode parallelisation patch spotted by SeanC, to > avoid scribbling on initial_gs in common_cpu_up(), and to allow all > 24 bits of the physical X2APIC ID to be used. That patch still needs > a Signed-off-by from its original author, who once claimed not to > remember writing it at all. But now we've fixed it, hopefully he'll > admit it now :) > v5: rebase to v6.1 and remeasure performance, disable parallel bringup > for AMD CPUs. Thanks, Usama. I've updated to v6.2-rc6 since there were a few more tweaks required (and we should double-check that the new handling of cache_ap_init from a dedicated cpuhp step works right if that ends up being done in parallel). I also fixed up the complaints from the test robot; including <linux/smpboot.h> from smpboot.c and making do_cpu_up() static, and putting #ifdef CONFIG_SMP around the 'are we booting the AP?' check and code segment in head_64.S. I've made the AMD thing a CPU bug as Peter suggested, and pushed it to https://git.infradead.org/users/dwmw2/linux.git/shortlog/refs/heads/parallel-6.2-rc6 for you to do the real work of actually testing it :)
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