From: Michael Ellerman <patch-notifications@ellerman.id.au>
To: Nicholas Piggin <npiggin@gmail.com>, linuxppc-dev@lists.ozlabs.org
Cc: "Aneesh Kumar K . V" <aneesh.kumar@linux.vnet.ibm.com>,
Nicholas Piggin <npiggin@gmail.com>
Subject: Re: [v4, 1/7] powerpc/64s/radix: do not flush TLB when relaxing access
Date: Tue, 5 Jun 2018 00:11:31 +1000 (AEST) [thread overview]
Message-ID: <40zxgm1t2Fz9s5c@ozlabs.org> (raw)
In-Reply-To: <20180601100121.393-2-npiggin@gmail.com>
On Fri, 2018-06-01 at 10:01:15 UTC, Nicholas Piggin wrote:
> Radix flushes the TLB when updating ptes to increase permissiveness
> of protection (increase access authority). Book3S does not require
> TLB flushing in this case, and it is not done on hash. This patch
> avoids the flush for radix.
>
> >From Power ISA v3.0B, p.1090:
>
> Setting a Reference or Change Bit or Upgrading Access Authority
> (PTE Subject to Atomic Hardware Updates)
>
> If the only change being made to a valid PTE that is subject to
> atomic hardware updates is to set the Reference or Change bit to 1
> or to add access authorities, a simpler sequence suffices because
> the translation hardware will refetch the PTE if an access is
> attempted for which the only problems were reference and/or change
> bits needing to be set or insufficient access authority.
>
> The nest MMU on POWER9 does not re-fetch the PTE after such an access
> attempt before faulting, so address spaces with a coprocessor
> attached will continue to flush in these cases.
>
> This reduces tlbies for a kernel compile workload from 1.28M to 0.95M,
> tlbiels from 20.17M 19.68M.
>
> fork --fork --exec benchmark improved 2.77% (12000->12300).
>
> Reviewed-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
> Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Series applied to powerpc next, thanks.
https://git.kernel.org/powerpc/c/e5f7cb58c2b77a0249c2028b6d1ec4
cheers
next prev parent reply other threads:[~2018-06-04 14:11 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-06-01 10:01 [PATCH v4 0/7] Various TLB and PTE improvements Nicholas Piggin
2018-06-01 10:01 ` [PATCH v4 1/7] powerpc/64s/radix: do not flush TLB when relaxing access Nicholas Piggin
2018-06-04 14:11 ` Michael Ellerman [this message]
2018-06-01 10:01 ` [PATCH v4 2/7] powerpc/64s/radix: do not flush TLB on spurious fault Nicholas Piggin
2018-06-01 10:01 ` [PATCH v4 3/7] powerpc/64s/radix: make ptep_get_and_clear_full non-atomic for the full case Nicholas Piggin
2018-06-01 10:01 ` [PATCH v4 4/7] powerpc/64s/radix: prefetch user address in update_mmu_cache Nicholas Piggin
2018-06-01 10:01 ` [PATCH v4 5/7] powerpc/64s/radix: avoid ptesync after set_pte and ptep_set_access_flags Nicholas Piggin
2018-06-01 10:01 ` [PATCH v4 6/7] powerpc/64s/radix: optimise pte_update Nicholas Piggin
2018-06-01 10:01 ` [PATCH v4 7/7] powerpc/64s/radix: flush remote CPUs out of single-threaded mm_cpumask Nicholas Piggin
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