Re: [PATCH v7 1/2] AVX512 support for xbzrle_encode_buffer

[Juan Quintela <quintela@redhat.com>]

ling xu <ling1.xu@intel.com> wrote:
> This commit is the same with [PATCH v6 1/2], and provides avx512 support for xbzrle_encode_buffer
> function to accelerate xbzrle encoding speed. Runtime check of avx512
> support and benchmark for this feature are added. Compared with C
> version of xbzrle_encode_buffer function, avx512 version can achieve
> 50%-70% performance improvement on benchmarking. In addition, if dirty
> data is randomly located in 4K page, the avx512 version can achieve
> almost 140% performance gain.
>
> Signed-off-by: ling xu <ling1.xu@intel.com>
> Co-authored-by: Zhou Zhao <zhou.zhao@intel.com>
> Co-authored-by: Jun Jin <jun.i.jin@intel.com>

Reviewed-by: Juan Quintela <quintela@redhat.com>

But there were a lot of "but's":

> diff --git a/meson.build b/meson.build
> index cf3e517e56..d0d28f5c9e 100644
> --- a/meson.build
> +++ b/meson.build
> @@ -2344,6 +2344,22 @@ config_host_data.set('CONFIG_AVX512F_OPT', get_option('avx512f') \
>      int main(int argc, char *argv[]) { return bar(argv[argc - 1]); }
>    '''), error_message: 'AVX512F not available').allowed())
>  
> +config_host_data.set('CONFIG_AVX512BW_OPT', get_option('avx512bw') \
> +  .require(have_cpuid_h, error_message: 'cpuid.h not available, cannot enable AVX512BW') \
> +  .require(cc.links('''
> +    #pragma GCC push_options
> +    #pragma GCC target("avx512bw")
> +    #include <cpuid.h>
> +    #include <immintrin.h>
> +    static int bar(void *a) {
> +
> +      __m512i *x = a;
> +      __m512i res= _mm512_abs_epi8(*x);
> +      return res[1];
> +    }
> +    int main(int argc, char *argv[]) { return bar(argv[0]); }
> +  '''), error_message: 'AVX512BW not available').allowed())
> +
>  have_pvrdma = get_option('pvrdma') \
>    .require(rdma.found(), error_message: 'PVRDMA requires OpenFabrics libraries') \
>    .require(cc.compiles(gnu_source_prefix + '''

This file misses:

@@ -3783,6 +3799,7 @@ summary_info += {'debug stack usage': get_option('debug_stack_usage')}
 summary_info += {'mutex debugging':   get_option('debug_mutex')}
 summary_info += {'memory allocator':  get_option('malloc')}
 summary_info += {'avx2 optimization': config_host_data.get('CONFIG_AVX2_OPT')}
+summary_info += {'avx512bw optimization': config_host_data.get('CONFIG_AVX512BW_OPT')}
 summary_info += {'avx512f optimization': config_host_data.get('CONFIG_AVX512F_OPT')}
 summary_info += {'gprof enabled':     get_option('gprof')}
 summary_info += {'gcov':              get_option('b_coverage')}
diff --git a/meson_options.txt b/meson_options.txt
index 559a571b6b..e5f199119e 100644
--- a/meson_options.txt
+++ b/meson_options.txt
@@ -104,6 +104,8 @@ option('avx2', type: 'feature', value: 'auto',
        description: 'AVX2 optimizations')
 option('avx512f', type: 'feature', value: 'disabled',
        description: 'AVX512F optimizations')
+option('avx512bw', type: 'feature', value: 'auto',
+       description: 'AVX512BW optimizations')
 option('keyring', type: 'feature', value: 'auto',
        description: 'Linux keyring support')

And you are missing:

diff --git a/scripts/meson-buildoptions.sh b/scripts/meson-buildoptions.sh
index 0f71e92dcb..c2982ea087 100644
--- a/scripts/meson-buildoptions.sh
+++ b/scripts/meson-buildoptions.sh
@@ -70,6 +70,7 @@ meson_options_help() {
   printf "%s\n" '  attr            attr/xattr support'
   printf "%s\n" '  auth-pam        PAM access control'
   printf "%s\n" '  avx2            AVX2 optimizations'
+  printf "%s\n" '  avx512bw        AVX512BW optimizations'
   printf "%s\n" '  avx512f         AVX512F optimizations'
   printf "%s\n" '  blkio           libblkio block device driver'
   printf "%s\n" '  bochs           bochs image format support'
@@ -198,6 +199,8 @@ _meson_option_parse() {
     --disable-auth-pam) printf "%s" -Dauth_pam=disabled ;;
     --enable-avx2) printf "%s" -Davx2=enabled ;;
     --disable-avx2) printf "%s" -Davx2=disabled ;;
+    --enable-avx512bw) printf "%s" -Davx512bw=enabled ;;
+    --disable-avx512bw) printf "%s" -Davx512bw=disabled ;;
     --enable-avx512f) printf "%s" -Davx512f=enabled ;;
     --disable-avx512f) printf "%s" -Davx512f=disabled ;;
     --enable-gcov) printf "%s" -Db_coverage=true ;;