[PATCH] configure: fix performance regression due to PIC objects

[PATCH] configure: fix performance regression due to PIC objects

[Paolo Bonzini]

Because most files in QEMU are grouped into static libraries, Meson conservatively
compiles them with -fPIC.  This is overkill and produces slowdowns up to 20% on
some TCG tests.

As a stopgap measure, use the b_staticpic option to limit the slowdown to
--enable-pie.  https://github.com/mesonbuild/meson/pull/7760 will allow
us to use b_staticpic=false and let Meson do the right thing.

Reported-by: Ahmed Karaman <ahmedkrmn@outlook.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 configure | 1 +
 1 file changed, 1 insertion(+)

diff --git a/configure b/configure
index 0004c46525..0786144043 100755
--- a/configure
+++ b/configure
@@ -7414,6 +7414,7 @@ NINJA=${ninja:-$PWD/ninjatool} $meson setup \
         -Dwerror=$(if test "$werror" = yes; then echo true; else echo false; fi) \
         -Dstrip=$(if test "$strip_opt" = yes; then echo true; else echo false; fi) \
         -Db_pie=$(if test "$pie" = yes; then echo true; else echo false; fi) \
+        -Db_staticpic=$(if test "$pie" = yes; then echo true; else echo false; fi) \
         -Db_coverage=$(if test "$gcov" = yes; then echo true; else echo false; fi) \
 	-Dmalloc=$malloc -Dmalloc_trim=$malloc_trim -Dsparse=$sparse \
 	-Dkvm=$kvm -Dhax=$hax -Dwhpx=$whpx -Dhvf=$hvf \
-- 
2.26.2

Re: [PATCH] configure: fix performance regression due to PIC objects

[Philippe Mathieu-Daudé]

Cc'ing Aleksandar as Ahmed is away.

On 9/19/20 5:56 PM, Paolo Bonzini wrote:
> Because most files in QEMU are grouped into static libraries, Meson conservatively
> compiles them with -fPIC.  This is overkill and produces slowdowns up to 20% on
> some TCG tests.
> 
> As a stopgap measure, use the b_staticpic option to limit the slowdown to
> --enable-pie.  https://github.com/mesonbuild/meson/pull/7760 will allow
> us to use b_staticpic=false and let Meson do the right thing.
> 
> Reported-by: Ahmed Karaman <ahmedkrmn@outlook.com>
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> ---
>  configure | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/configure b/configure
> index 0004c46525..0786144043 100755
> --- a/configure
> +++ b/configure
> @@ -7414,6 +7414,7 @@ NINJA=${ninja:-$PWD/ninjatool} $meson setup \
>          -Dwerror=$(if test "$werror" = yes; then echo true; else echo false; fi) \
>          -Dstrip=$(if test "$strip_opt" = yes; then echo true; else echo false; fi) \
>          -Db_pie=$(if test "$pie" = yes; then echo true; else echo false; fi) \
> +        -Db_staticpic=$(if test "$pie" = yes; then echo true; else echo false; fi) \
>          -Db_coverage=$(if test "$gcov" = yes; then echo true; else echo false; fi) \
>  	-Dmalloc=$malloc -Dmalloc_trim=$malloc_trim -Dsparse=$sparse \
>  	-Dkvm=$kvm -Dhax=$hax -Dwhpx=$whpx -Dhvf=$hvf \
> 

Re: [PATCH] configure: fix performance regression due to PIC objects

[Richard Henderson]

On 9/19/20 8:56 AM, Paolo Bonzini wrote:
> Because most files in QEMU are grouped into static libraries, Meson conservatively
> compiles them with -fPIC.  This is overkill and produces slowdowns up to 20% on
> some TCG tests.
> 
> As a stopgap measure, use the b_staticpic option to limit the slowdown to
> --enable-pie.  https://github.com/mesonbuild/meson/pull/7760 will allow
> us to use b_staticpic=false and let Meson do the right thing.
> 
> Reported-by: Ahmed Karaman <ahmedkrmn@outlook.com>
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> ---
>  configure | 1 +
>  1 file changed, 1 insertion(+)

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>

r~