On 07/11/2016 13:49, Stefan Hajnoczi wrote: > On Wed, Nov 02, 2016 at 05:24:01PM +0100, Paolo Bonzini wrote: >> Unnesting variables spends a lot of time parsing and executing foreach >> and if functions. Because actually very few variables have to be >> saved and restored, a good strategy is to remember what has to be done >> in load-vars, and only iterate the right variables in load-vars. >> For save-vars, unroll the foreach loop to provide another small >> improvement. >> >> This speeds up a "noop" build from around 15.5 seconds on my laptop >> to 11.7 (25% roughly). >> >> Signed-off-by: Paolo Bonzini <pbonz...@redhat.com> >> --- >> I'm wondering if this would be acceptable for 2.8. >> I also have sent patches to GNU make that save another >> 20%, down to 9.8 seconds. > > Sorry but I'd like to stick to the soft freeze policy. This patch is a > nice improvement but it's not a bug fix. Let's merge it for 2.9.
Fine by me, thanks! Paolo >> rules.mak | 22 ++++++++++------------ >> 1 file changed, 10 insertions(+), 12 deletions(-) >> >> diff --git a/rules.mak b/rules.mak >> index 0333ae3..c0777d7 100644 >> --- a/rules.mak >> +++ b/rules.mak >> @@ -192,15 +192,15 @@ clean: clean-timestamp >> # save-vars >> # Usage: $(call save-vars, vars) >> # Save each variable $v in $vars as save-vars-$v, save their object's >> -# variables, then clear $v. >> +# variables, then clear $v. saved-vars-$v caches the list of variables >> +# that were saved for the objects, in order to speedup load-vars. >> define save-vars >> $(foreach v,$1, >> $(eval save-vars-$v := $(value $v)) >> - $(foreach o,$($v), >> - $(foreach k,cflags libs objs, >> - $(if $($o-$k), >> - $(eval save-vars-$o-$k := $($o-$k)) >> - $(eval $o-$k := )))) >> + $(eval saved-vars-$v := $(foreach o,$($v), \ >> + $(if $($o-cflags), $o-cflags $(eval save-vars-$o-cflags := >> $($o-cflags))$(eval $o-cflags := )) \ >> + $(if $($o-libs), $o-libs $(eval save-vars-$o-libs := >> $($o-libs))$(eval $o-libs := )) \ >> + $(if $($o-objs), $o-objs $(eval save-vars-$o-objs := >> $($o-objs))$(eval $o-objs := )))) >> $(eval $v := )) >> endef >> >> @@ -213,12 +213,10 @@ define load-vars >> $(eval $2-new-value := $(value $2)) >> $(foreach v,$1, >> $(eval $v := $(value save-vars-$v)) >> - $(foreach o,$($v), >> - $(foreach k,cflags libs objs, >> - $(if $(save-vars-$o-$k), >> - $(eval $o-$k := $(save-vars-$o-$k)) >> - $(eval save-vars-$o-$k := )))) >> - $(eval save-vars-$v := )) >> + $(foreach o,$(saved-vars-$v), >> + $(eval $o := $(save-vars-$o)) $(eval save-vars-$o := )) >> + $(eval save-vars-$v := ) >> + $(eval saved-vars-$v := )) >> $(eval $2 := $(value $2) $($2-new-value)) >> endef >> >> -- >> 2.7.4 >> >>
