From: Catalin Marinas <catalin.marinas@arm.com>
To: Julien Grall <julien.grall@arm.com>
Cc: julien.thierry@arm.com, marc.zyngier@arm.com,
suzuki.poulose@arm.com, will.deacon@arm.com,
linux-kernel@vger.kernel.org, james.morse@arm.com,
kvmarm@lists.cs.columbia.edu,
linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v3 09/15] arm64/mm: Split the function check_and_switch_context in 3 parts
Date: Thu, 25 Jul 2019 17:28:28 +0100 [thread overview]
Message-ID: <20190725162827.GE4113@arrakis.emea.arm.com> (raw)
In-Reply-To: <20190724162534.7390-10-julien.grall@arm.com>
On Wed, Jul 24, 2019 at 05:25:28PM +0100, Julien Grall wrote:
> The function check_and_switch_context is used to:
> 1) Check whether the ASID is still valid
> 2) Generate a new one if it is not valid
> 3) Switch the context
>
> While the latter is specific to the MM subsystem, the rest could be part
> of the generic ASID allocator.
>
> After this patch, the function is now split in 3 parts which corresponds
> to the use of the functions:
> 1) asid_check_context: Check if the ASID is still valid
> 2) asid_new_context: Generate a new ASID for the context
> 3) check_and_switch_context: Call 1) and 2) and switch the context
>
> 1) and 2) have not been merged in a single function because we want to
> avoid to add a branch in when the ASID is still valid. This will matter
> when the code will be moved in separate file later on as 1) will reside
> in the header as a static inline function.
>
> Signed-off-by: Julien Grall <julien.grall@arm.com>
>
> ---
> Will wants to avoid to add a branch when the ASID is still valid. So
> 1) and 2) are in separates function. The former will move to a new
> header and make static inline.
Was this discussion logged somewhere, just to get the context?
I presume by "branch" you meant the function call to
asid_check_context(). Personally, I don't like the duplication of this
function in patch 13. This is part of the ASID allocation algorithm and
I prefer to keep them together (we even had a bug in here with the xchg
use).
Do you have any numbers to show how non-inlining this function affects
the performance (hackbench -P would do).
--
Catalin
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next prev parent reply other threads:[~2019-07-25 16:29 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-24 16:25 [PATCH v3 00/15] kvm/arm: Align the VMID allocation with the arm64 ASID one Julien Grall
2019-07-24 16:25 ` [PATCH v3 01/15] arm64/mm: Introduce asid_info structure and move asid_generation/asid_map to it Julien Grall
2019-07-24 16:25 ` [PATCH v3 02/15] arm64/mm: Move active_asids and reserved_asids to asid_info Julien Grall
2019-07-24 16:25 ` [PATCH v3 03/15] arm64/mm: Move bits " Julien Grall
2019-07-24 16:25 ` [PATCH v3 04/15] arm64/mm: Move the variable lock and tlb_flush_pending " Julien Grall
2019-07-24 16:25 ` [PATCH v3 05/15] arm64/mm: Remove dependency on MM in new_context Julien Grall
2019-07-24 16:25 ` [PATCH v3 06/15] arm64/mm: Store the number of asid allocated per context Julien Grall
2019-07-24 16:25 ` [PATCH v3 07/15] arm64/mm: Introduce NUM_ASIDS Julien Grall
2019-07-24 16:25 ` [PATCH v3 08/15] arm64/mm: Split asid_inits in 2 parts Julien Grall
2019-07-24 16:25 ` [PATCH v3 09/15] arm64/mm: Split the function check_and_switch_context in 3 parts Julien Grall
2019-07-25 16:28 ` Catalin Marinas [this message]
2019-07-24 16:25 ` [PATCH v3 10/15] arm64/mm: Introduce a callback to flush the local context Julien Grall
2019-07-24 16:25 ` [PATCH v3 11/15] arm64: Move the ASID allocator code in a separate file Julien Grall
2019-07-24 16:25 ` [PATCH v3 12/15] arm64/lib: Add an helper to free memory allocated by the ASID allocator Julien Grall
2019-07-24 16:25 ` [PATCH v3 13/15] arm/kvm: Introduce a new VMID allocator Julien Grall
2019-07-24 16:25 ` [PATCH v3 14/15] arch/arm64: Introduce a capability to tell whether 16-bit VMID is available Julien Grall
2019-07-24 16:25 ` [PATCH v3 15/15] kvm/arm: Align the VMID allocation with the arm64 ASID one Julien Grall
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