Messages in this thread | | | Date | Thu, 25 Apr 2019 13:17:37 -0700 (PDT) | Subject | Re: [1/3] x86: Update DEBUG_TLBFLUSH options description. | From | Palmer Dabbelt <> |
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On Wed, 10 Apr 2019 15:44:47 PDT (-0700), atish.patra@wdc.com wrote: > CONFIG_DEBUG_TLBFLUSH was added in 'commit 3df3212f9722 ("x86/tlb: add > tlb_flushall_shift knob into debugfs")' to support tlb_flushall_shift > knob. The knob was removed in 'commit e9f4e0a9fe27 ("x86/mm: Rip out > complicated, out-of-date, buggy TLB flushing")'. However, the debug > option was never removed from Kconfig. It was reused in commit > '9824cf9753ec ("mm: vmstats: tlb flush counters")' but the commit text was > never updated accordingly. > > Update the Kconfig option description as per its current usage. > > Signed-off-by: Atish Patra <atish.patra@wdc.com> > --- > arch/x86/Kconfig.debug | 15 +++------------ > 1 file changed, 3 insertions(+), 12 deletions(-) > > diff --git a/arch/x86/Kconfig.debug b/arch/x86/Kconfig.debug > index 15d0fbe27872..c1a48d4ffebb 100644 > --- a/arch/x86/Kconfig.debug > +++ b/arch/x86/Kconfig.debug > @@ -125,21 +125,12 @@ config DOUBLEFAULT > hair. > > config DEBUG_TLBFLUSH > - bool "Set upper limit of TLB entries to flush one-by-one" > + bool "Save tlb flush statstics to vmstat" > depends on DEBUG_KERNEL > ---help--- > > - X86-only for now. > - > - This option allows the user to tune the amount of TLB entries the > - kernel flushes one-by-one instead of doing a full TLB flush. In > - certain situations, the former is cheaper. This is controlled by the > - tlb_flushall_shift knob under /sys/kernel/debug/x86. If you set it > - to -1, the code flushes the whole TLB unconditionally. Otherwise, > - for positive values of it, the kernel will use single TLB entry > - invalidating instructions according to the following formula: > - > - flush_entries <= active_tlb_entries / 2^tlb_flushall_shift > + Add tlbflush statstics to vmstat. It is really helpful understand tlbflush > + performance and behavior. It should be enabled only for debugging purpose. > > If in doubt, say "N".
Reviewed-by: Palmer Dabbelt <palmer@sifivee.com>
I'm not going to take this via my tree, but I'll look into the next two.
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