| Message ID | 20190410224449.10877-2-atish.patra@wdc.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | TLB flush counters | expand |
Given that this option enables generic code (which you reuse for RISC-V later in this series) please also move the config option to mm/Kconfig, proabbly keyed off another ARCH_HAVE_DEBUG_TLBFLUSH symbol that the architecture can select.
On 4/10/19 11:56 PM, Christoph Hellwig wrote: > Given that this option enables generic code (which you reuse for RISC-V > later in this series) please also move the config option to > mm/Kconfig, proabbly keyed off another ARCH_HAVE_DEBUG_TLBFLUSH > symbol that the architecture can select. > Sure. Regards, Atish > _______________________________________________ > linux-riscv mailing list > linux-riscv@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/linux-riscv >
On Fri, Apr 12, 2019 at 01:14:54PM -0700, Atish Patra wrote: > On 4/10/19 11:56 PM, Christoph Hellwig wrote: > > Given that this option enables generic code (which you reuse for RISC-V > > later in this series) please also move the config option to > > mm/Kconfig, proabbly keyed off another ARCH_HAVE_DEBUG_TLBFLUSH > > symbol that the architecture can select. > > > > Sure. And when you do that, instead of deleting the help text, make it generic. Otherwise, there's no explanation anymore, how that option is supposed to be used through tlb_flushall_shift.
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 complicated, out-of-date, buggy TLB flushing")'.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.
On 4/14/19 7:29 AM, Borislav Petkov wrote: > On Fri, Apr 12, 2019 at 01:14:54PM -0700, Atish Patra wrote: >> On 4/10/19 11:56 PM, Christoph Hellwig wrote: >>> Given that this option enables generic code (which you reuse for RISC-V >>> later in this series) please also move the config option to >>> mm/Kconfig, proabbly keyed off another ARCH_HAVE_DEBUG_TLBFLUSH >>> symbol that the architecture can select. >>> >> >> Sure. > > And when you do that, instead of deleting the help text, make it > generic. Otherwise, there's no explanation anymore, how that option is > supposed to be used through tlb_flushall_shift. > Not sure I am following you. tlb_flushall_shift knob was removed by commit e9f4e0a9fe27 ("x86/mm: Rip out complicated, out-of-date, buggy TLB flushing") Regards, Atish
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".
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(-)