From: Adhemerval Zanella Netto <adhemerval.zanella@linaro.org>
To: Palmer Dabbelt <palmer@rivosinc.com>
Cc: Evan Green <evan@rivosinc.com>,
libc-alpha@sourceware.org, slewis@rivosinc.com,
Vineet Gupta <vineetg@rivosinc.com>
Subject: Re: [PATCH v2 0/3] RISC-V: ifunced memcpy using new kernel hwprobe interface
Date: Wed, 29 Mar 2023 16:16:39 -0300 [thread overview]
Message-ID: <c7678c7d-a792-3ce3-55cf-43712acb0703@linaro.org> (raw)
In-Reply-To: <mhng-8b4e5bc5-b610-4c82-98a6-03d6d9b136e1@palmer-ri-x1c9a>
On 28/03/23 21:01, Palmer Dabbelt wrote:
> On Tue, 28 Mar 2023 16:41:10 PDT (-0700), adhemerval.zanella@linaro.org wrote:
>>
>>
>> On 28/03/23 19:54, Palmer Dabbelt wrote:
>>> On Tue, 21 Feb 2023 11:15:34 PST (-0800), Evan Green wrote:
>>>>
>>>> This series illustrates the use of a proposed Linux syscall that
>>>> enumerates architectural information about the RISC-V cores the system
>>>> is running on. In this series we expose a small wrapper function around
>>>> the syscall. An ifunc selector for memcpy queries it to see if unaligned
>>>> access is "fast" on this hardware. If it is, it selects a newly provided
>>>> implementation of memcpy that doesn't work hard at aligning the src and
>>>> destination buffers.
>>>>
>>>> This is somewhat of a proof of concept for the syscall itself, but I do
>>>> find that in my goofy memcpy test [1], the unaligned memcpy performed at
>>>> least as well as the generic C version. This is however on Qemu on an M1
>>>> mac, so not a test of any real hardware (more a smoke test that the
>>>> implementation isn't silly).
>>>
>>> QEMU isn't a good enough benchmark to justify a new memcpy routine in glibc. Evan has a D1, which does support misaligned access and runs some simple benchmarks faster. There's also been some minor changes to the Linux side of things that warrant a v3 anyway, so he'll just post some benchmarks on HW along with that.
>>>
>>> Aside from those comments,
>>>
>>> Reviewed-by: Palmer Dabbelt <palmer@rivosinc.com>
>>>
>>> There's a lot more stuff to probe for, but I think we've got enough of a proof of concept for the hwprobe stuff that we can move forward with the core interface bits in Linux/glibc and then unleash the chaos...
>>>
>>> Unless anyone else has comments?
>>
>> Until riscv_hwprobe is not on Linus tree as official Linux ABI this patchset
>> can not be installed. We failed to enforce it on some occasion (like Intel
>> CET) and it turned out a complete mess after some years...
>
> Sorry if that wasn't clear, I was asking if there were any more comments from the glibc side of things before merging the Linux code.
Right, so is this already settle to be the de-factor ABI to query for system
information in RISCV? Or is it still being discussed? Is it in a next branch
already, and/or have been tested with a patch glibc?
In any case I added some minimal comments. With the vDSO approach I think
there is no need to cache the result at startup, as aarch64 and x86 does.
next prev parent reply other threads:[~2023-03-29 19:16 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-02-21 19:15 Evan Green
2023-02-21 19:15 ` [PATCH v2 1/3] riscv: Add Linux hwprobe syscall support Evan Green
2023-03-29 18:38 ` Adhemerval Zanella Netto
2023-02-21 19:15 ` [PATCH v2 2/3] riscv: Add hwprobe vdso call support Evan Green
2023-03-29 18:39 ` Adhemerval Zanella Netto
2023-02-21 19:15 ` [PATCH v2 3/3] riscv: Add and use alignment-ignorant memcpy Evan Green
2023-03-28 22:54 ` [PATCH v2 0/3] RISC-V: ifunced memcpy using new kernel hwprobe interface Palmer Dabbelt
2023-03-28 23:41 ` Adhemerval Zanella Netto
2023-03-29 0:01 ` Palmer Dabbelt
2023-03-29 19:16 ` Adhemerval Zanella Netto [this message]
2023-03-29 19:45 ` Palmer Dabbelt
2023-03-29 20:13 ` Adhemerval Zanella Netto
2023-03-30 18:31 ` Evan Green
2023-03-30 19:43 ` Adhemerval Zanella Netto
2023-03-30 6:20 ` Jeff Law
2023-03-30 18:43 ` Evan Green
2023-03-31 5:09 ` Jeff Law
2023-03-30 19:38 ` Adhemerval Zanella Netto
2023-03-31 18:07 ` Jeff Law
2023-03-31 18:34 ` Palmer Dabbelt
2023-03-31 19:32 ` Adhemerval Zanella Netto
2023-03-31 20:19 ` Jeff Law
2023-03-31 21:03 ` Palmer Dabbelt
2023-03-31 21:35 ` Jeff Law
2023-03-31 21:38 ` Palmer Dabbelt
2023-03-31 22:10 ` Jeff Law
2023-04-07 15:36 ` Palmer Dabbelt
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