From: Robert Hoo <robert.hu@linux.intel.com>
To: Richard Henderson <richard.henderson@linaro.org>,
qemu-devel@nongnu.org, pbonzini@redhat.com, laurent@vivier.eu,
philmd@redhat.com, berrange@redhat.com
Cc: robert.hu@intel.com
Subject: Re: [PATCH 2/2] util: add util function buffer_zero_avx512()
Date: Tue, 25 Feb 2020 15:34:07 +0800 [thread overview]
Message-ID: <1c4cf8366513c96063d7f6e2bc9d2e959ad08d6c.camel@linux.intel.com> (raw)
In-Reply-To: <7b8fd7a0-9cb8-aab8-0f1b-4a77dd7a6378@linaro.org>
On Mon, 2020-02-24 at 08:13 -0800, Richard Henderson wrote:
> On 2/23/20 11:07 PM, Robert Hoo wrote:
> > Inspired by your suggestion, I'm thinking go further: use immediate
> > rather than a global variable, so that saves 1 memory(/cache)
> > access.
> >
> > #ifdef CONFIG_AVX512F_OPT
> > #define OPTIMIZE_LEN 256
> > #else
> > #define OPTIMIZE_LEN 64
> > #endif
>
> With that, the testing in tests/test-bufferiszero.c, looping through
> the
> implementations, is invalidated. Because once you start compiling
> for avx512,
> you're no longer testing sse2 et al with the same inputs.
>
Right. Thanks pointing out. I didn't noticed that.
More precisely, it would cause no longer testing sse2 et al with < 256
length.
> IF we want to change the length to suit avx512, we would want to
> change it
> unconditionally. And then you could also tidy up avx2 to avoid the
> extra
> comparisons there.
Considering the length's dependency on sse2/sse4/avx2/avx512 and the
algorithms, as well as future's possible changes, additions, I'd rather
roll back to your original suggestion, use a companion variable with
each accel_fn(). How do you like it?
>
>
> r~
next prev parent reply other threads:[~2020-02-25 7:34 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-13 7:52 [PATCH 0/2] Add AVX512F optimization option and buffer_zero_avx512() Robert Hoo
2020-02-13 7:52 ` [PATCH 1/2] configure: add configure option avx512f_opt Robert Hoo
2020-02-13 7:52 ` [PATCH 2/2] util: add util function buffer_zero_avx512() Robert Hoo
2020-02-13 10:30 ` Paolo Bonzini
2020-02-13 11:58 ` Robert Hoo
2020-02-13 18:20 ` Richard Henderson
2020-02-24 7:07 ` Robert Hoo
2020-02-24 16:13 ` Richard Henderson
2020-02-25 7:34 ` Robert Hoo [this message]
2020-02-25 15:29 ` Richard Henderson
2020-02-13 8:40 ` [PATCH 0/2] Add AVX512F optimization option and buffer_zero_avx512() no-reply
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