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From:   David Howells <dhowells@redhat.com>
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To:     Borislav Petkov <bp@alien8.de>
Cc:     dhowells@redhat.com,
        Linus Torvalds <torvalds@linux-foundation.org>,
        kernel test robot <oliver.sang@intel.com>,
        oe-lkp@lists.linux.dev, lkp@intel.com,
        linux-kernel@vger.kernel.org,
        Christian Brauner <brauner@kernel.org>,
        Alexander Viro <viro@zeniv.linux.org.uk>,
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        Matthew Wilcox <willy@infradead.org>,
        David Laight <David.Laight@aculab.com>, ying.huang@intel.com,
        feng.tang@intel.com, fengwei.yin@intel.com
Subject: Re: [linus:master] [iov_iter] c9eec08bac: vm-scalability.throughput -16.9% regression
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Date:   Thu, 16 Nov 2023 16:44:06 +0000
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Borislav Petkov <bp@alien8.de> wrote:

> diff --git a/Makefile b/Makefile
> index ede0bd241056..94d93070d54a 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -996,6 +996,8 @@ endif
>  # change __FILE__ to the relative path from the srctree
>  KBUILD_CPPFLAGS +=3D $(call cc-option,-fmacro-prefix-map=3D$(srctree)/=3D=
)
>  =

> +KBUILD_CFLAGS	+=3D $(call cc-option,-mstringop-strategy=3Dlibcall)
> +
>  # include additional Makefiles when needed
>  include-y			:=3D scripts/Makefile.extrawarn
>  include-$(CONFIG_DEBUG_INFO)	+=3D scripts/Makefile.debug

If you wanted this patch trying, I get the following numbers:

 iov_kunit_benchmark_bvec: avg 9950 uS, stddev 40 uS
 iov_kunit_benchmark_bvec: avg 9950 uS, stddev 53 uS
 iov_kunit_benchmark_bvec: avg 9973 uS, stddev 69 uS
 iov_kunit_benchmark_bvec_split: avg 9793 uS, stddev 28 uS
 iov_kunit_benchmark_bvec_split: avg 9800 uS, stddev 41 uS
 iov_kunit_benchmark_bvec_split: avg 9804 uS, stddev 16 uS
 iov_kunit_benchmark_kvec: avg 10122 uS, stddev 4403 uS
 iov_kunit_benchmark_kvec: avg 9757 uS, stddev 1516 uS
 iov_kunit_benchmark_kvec: avg 9909 uS, stddev 2694 uS
 iov_kunit_benchmark_xarray: avg 10526 uS, stddev 52 uS
 iov_kunit_benchmark_xarray: avg 10529 uS, stddev 48 uS
 iov_kunit_benchmark_xarray: avg 10532 uS, stddev 63 uS
 iov_kunit_benchmark_xarray_to_bvec: avg 10468 uS, stddev 23 uS
 iov_kunit_benchmark_xarray_to_bvec: avg 10469 uS, stddev 157 uS
 iov_kunit_benchmark_xarray_to_bvec: avg 10471 uS, stddev 163 uS

I'm using the 6 patches here:

	https://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs.git/log=
/?h=3Diov-kunit

Set CONFIG_TEST_IOV_ITER=3Dm and then load the kunit_iov_iter.ko module.  =
It'll
dump its benchmarks to dmesg.

David