From: Richard Henderson <richard.henderson@linaro.org>
To: Alexander Monakov <amonakov@ispras.ru>, qemu-devel@nongnu.org
Cc: Mikhail Romanov <mmromanov@ispras.ru>,
Paolo Bonzini <pbonzini@redhat.com>
Subject: Re: [PATCH v3 4/6] util/bufferiszero: remove useless prefetches
Date: Wed, 7 Feb 2024 08:29:18 +1000 [thread overview]
Message-ID: <14b49de5-67d7-46f1-9e15-be60fb925dd3@linaro.org> (raw)
In-Reply-To: <20240206204809.9859-5-amonakov@ispras.ru>
On 2/7/24 06:48, Alexander Monakov wrote:
> Use of prefetching in bufferiszero.c is quite questionable:
>
> - prefetches are issued just a few CPU cycles before the corresponding
> line would be hit by demand loads;
>
> - they are done for simple access patterns, i.e. where hardware
> prefetchers can perform better;
>
> - they compete for load ports in loops that should be limited by load
> port throughput rather than ALU throughput.
>
> Signed-off-by: Alexander Monakov<amonakov@ispras.ru>
> Signed-off-by: Mikhail Romanov<mmromanov@ispras.ru>
> ---
> util/bufferiszero.c | 3 ---
> 1 file changed, 3 deletions(-)
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
r~
next prev parent reply other threads:[~2024-02-06 22:30 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-02-06 20:48 [PATCH v3 0/6] Optimize buffer_is_zero Alexander Monakov
2024-02-06 20:48 ` [PATCH v3 1/6] util/bufferiszero: remove SSE4.1 variant Alexander Monakov
2024-02-06 22:24 ` Richard Henderson
2024-02-06 20:48 ` [PATCH v3 2/6] util/bufferiszero: introduce an inline wrapper Alexander Monakov
2024-02-06 22:44 ` Richard Henderson
2024-02-07 7:13 ` Alexander Monakov
2024-02-08 20:07 ` Richard Henderson
2024-02-06 20:48 ` [PATCH v3 3/6] util/bufferiszero: remove AVX512 variant Alexander Monakov
2024-02-06 22:28 ` Richard Henderson
2024-02-06 23:56 ` Elena Ufimtseva
2024-02-07 6:29 ` Alexander Monakov
2024-02-07 10:38 ` Joao Martins
2024-02-06 20:48 ` [PATCH v3 4/6] util/bufferiszero: remove useless prefetches Alexander Monakov
2024-02-06 22:29 ` Richard Henderson [this message]
2024-02-06 20:48 ` [PATCH v3 5/6] util/bufferiszero: optimize SSE2 and AVX2 variants Alexander Monakov
2024-02-06 23:10 ` Richard Henderson
2024-02-06 20:48 ` [PATCH v3 6/6] util/bufferiszero: improve scalar variant Alexander Monakov
2024-02-06 22:34 ` Richard Henderson
2024-02-06 22:46 ` Richard Henderson
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