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List: fedora-devel-list
Subject: Re: Fedora 32 System-Wide Change proposal: x86-64 micro-architecture update
From: Frantisek Zatloukal <fzatlouk () redhat ! com>
Date: 2019-07-31 13:13:51
Message-ID: CACBV9ZhOJ+yQwwMtDVDPf+qXa7d8RN4R9=1=1iL=+P7JczBgeg () mail ! gmail ! com
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Personally, I am not at all against raising the bar for baseline x86_64. Of
course, it'd be ideal to have some sort of derived x86_64_avx arch, but if
we find out it'd require too much of an investment into infra/releng, I'd
be +1 for just changing the base x86_64. Sure, it'd make sense to actually
see some numbers from Fedora compiled with SSE4/AVX/AVX2 and not just guess
from Clear Linux results.
I see AVX2 is just too high baseline (although, all my PCs and laptops
support that for at least 2 years), but raising the baseline to something
like AVX or SSE4 might make sense. I don't know why people with *not
ancient* computers should have degraded performance just because we want to
support everything from K8 from 2003. But as I said, it'd be nice to see
some benchmarks to base the decision on and have optimized x86_64 as
secondary arch, if possible.
On Wed, Jul 31, 2019 at 11:00 AM Kevin Kofler <kevin.kofler@chello.at>
wrote:
> * the performance increase to be had is marginal, given that we are mostly
> talking about code written in C or C++ without even compiler
> vectorization
> (-ftree-vectorize) turned on,
>
Are you sure? Fore example (and there are more of them), lots of these do
not seem marginal:
https://www.phoronix.com/scan.php?page=news_item&px=Clear-Linux-2019-Python-Perf
, https://www.phoronix.com/scan.php?page=article&item=linux-2016-2018&num=3
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<div dir="ltr"><div>Personally, I am not at all against raising the bar for baseline \
x86_64. Of course, it'd be ideal to have some sort of derived x86_64_avx arch, \
but if we find out it'd require too much of an investment into infra/releng, \
I'd be +1 for just changing the base x86_64. Sure, it'd make sense to \
actually see some numbers from Fedora compiled with SSE4/AVX/AVX2 and not just guess \
from Clear Linux results.</div><div><br></div><div>I see AVX2 is just too high \
baseline (although, all my PCs and laptops support that for at least 2 years), but \
raising the baseline to something like AVX or SSE4 might make sense. I don't know \
why people with *not ancient* computers should have degraded performance just because \
we want to support everything from K8 from 2003. But as I said, it'd be nice to \
see some benchmarks to base the decision on and have optimized x86_64 as secondary \
arch, if possible. </div><div dir="ltr"><br></div><div dir="ltr">On Wed, Jul 31, \
2019 at 11:00 AM Kevin Kofler <<a \
href="mailto:kevin.kofler@chello.at">kevin.kofler@chello.at</a>> wrote:</div><div \
class="gmail_quote"><blockquote class="gmail_quote" style="margin:0px 0px 0px \
0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
* the performance increase to be had is marginal, given that we are mostly<br>
talking about code written in C or C++ without even compiler vectorization<br>
(-ftree-vectorize) turned on,<br></blockquote><div><br></div><div>Are you sure? \
Fore example (and there are more of them), lots of these do not seem marginal: <a \
href="https://www.phoronix.com/scan.php?page=news_item&px=Clear-Linux-2019-Python- \
Perf">https://www.phoronix.com/scan.php?page=news_item&px=Clear-Linux-2019-Python-Perf</a> \
, <a href="https://www.phoronix.com/scan.php?page=article&item=linux-2016-2018&am \
p;num=3">https://www.phoronix.com/scan.php?page=article&item=linux-2016-2018&num=3</a></div><div><br></div><div><br></div><div><br></div></div></div>
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