Le Wed, Oct 29, 2025 at 11:16:23AM +0100, Valentin Schneider a écrit : > On 28/10/25 16:59, Frederic Weisbecker wrote: > > Le Fri, Oct 10, 2025 at 05:38:37PM +0200, Valentin Schneider a écrit : > >> @@ -171,8 +172,27 @@ For 32-bit we have the following conventions - kernel > >> is built with > >> andq $(~PTI_USER_PGTABLE_AND_PCID_MASK), \reg > >> .endm > >> > >> -.macro COALESCE_TLBI > >> +.macro COALESCE_TLBI scratch_reg:req > >> #ifdef CONFIG_COALESCE_TLBI > >> + /* No point in doing this for housekeeping CPUs */ > >> + movslq PER_CPU_VAR(cpu_number), \scratch_reg > >> + bt \scratch_reg, tick_nohz_full_mask(%rip) > >> + jnc .Lend_tlbi_\@ > > > > I assume it's not possible to have a static call/branch to > > take care of all this ? > > > > I think technically yes, but that would have to be a per-cpu patchable > location, which would mean something like each CPU having its own copy of > that text page... Unless there's some existing way to statically optimize > > if (cpumask_test_cpu(smp_processor_id(), mask)) > > where @mask is a boot-time constant (i.e. the nohz_full mask).
Or just check housekeeping_overriden static key before everything. This one is enabled only if either nohz_full, isolcpus or cpuset isolated partition (well, it's on the way for the last one) are running, but those are all niche, which means you spare 99.999% kernel usecases. Thanks. > > > Thanks. > > > > -- > > Frederic Weisbecker > > SUSE Labs > > -- Frederic Weisbecker SUSE Labs
