[U-Boot] [U-Boot, 1/2] common: Add CCACHE variable to allow use of ccache

[Marek Vasut]

Dear sun york-R58495,

> On Aug 21, 2013, at 10:45 PM, sun york-R58495 wrote:
> > On Aug 21, 2013, at 10:02 PM, Marek Vasut wrote:
> >> Dear sun york-R58495,
> >> 
> >>> On Aug 21, 2013, at 7:51 PM, Marek Vasut wrote:
> >>>> Dear York Sun,
> >>>> 
> >>>>> On 05/20/2013 10:25 AM, Marek Vasut wrote:
> >>>>>> Prefix HOSTCC and CC with CCACHE variable to allow easy use of
> >>>>>> ccache. In case the user wants to use ccache, exporting
> >>>>>> CCACHE=ccache will do the trick. It is of course possible to either
> >>>>>> make the cross-compiler name into a shellscript which invokes the
> >>>>>> ccache and the compiler, but setting this variable makes use of
> >>>>>> ccache easier and more convenient.
> >>>>>> 
> >>>>>> Using ccache becomes convenient when using MAKEALL for large build
> >>>>>> tests, where the speedup after building the cache for the first time
> >>>>>> is about 4-6 times.
> >>>>>> 
> >>>>>> Signed-off-by: Marek Vasut <marex at denx.de>
> >>>>>> Cc: Tom Rini <trini at ti.com>
> >>>>>> 
> >>>>>> ---
> >>>>>> config.mk |    8 +++++---
> >>>>>> 
> >>>>>> 1 file changed, 5 insertions(+), 3 deletions(-)
> >>>>>> 
> >>>>>> diff --git a/config.mk b/config.mk
> >>>>>> index 1fd109f..d59ded2 100644
> >>>>>> --- a/config.mk
> >>>>>> +++ b/config.mk
> >>>>>> @@ -98,6 +98,8 @@ else
> >>>>>> 
> >>>>>> HOSTCC		= gcc
> >>>>>> endif
> >>>>>> 
> >>>>>> +HOSTCC		:= $(CCACHE) $(HOSTCC)
> >>>>>> +
> >>>>>> 
> >>>>>> ifeq ($(HOSTOS),cygwin)
> >>>>>> HOSTCFLAGS	+= -ansi
> >>>>>> endif
> >>>>>> 
> >>>>>> @@ -140,13 +142,13 @@ binutils-version = $(shell $(SHELL)
> >>>>>> $(SRCTREE)/tools/binutils-version.sh $(AS))
> >>>>>> 
> >>>>>> #
> >>>>>> # Include the make variables (CC, etc...)
> >>>>>> #
> >>>>>> 
> >>>>>> -AS	= $(CROSS_COMPILE)as
> >>>>>> +AS	= $(CCACHE) $(CROSS_COMPILE)as
> >>>>>> 
> >>>>>> # Always use GNU ld
> >>>>>> LD	= $(shell if $(CROSS_COMPILE)ld.bfd -v > /dev/null 2>&1; \
> >>>>>> 
> >>>>>> 		then echo "$(CROSS_COMPILE)ld.bfd"; else echo
> >>>> 
> >>>> "$(CROSS_COMPILE)ld";
> >>>> 
> >>>>>> 		fi;)
> >>>>>> 
> >>>>>> -CC	= $(CROSS_COMPILE)gcc
> >>>>>> +CC	= $(CCACHE) $(CROSS_COMPILE)gcc
> >>>>>> 
> >>>>>> CPP	= $(CC) -E
> >>>>>> AR	= $(CROSS_COMPILE)ar
> >>>>>> NM	= $(CROSS_COMPILE)nm
> >>>>>> 
> >>>>>> @@ -320,7 +322,7 @@ endif
> >>>>>> 
> >>>>>> ####################################################################
> >>>>>> ### # #
> >>>>>> 
> >>>>>> -export	HOSTCC HOSTCFLAGS HOSTLDFLAGS PEDCFLAGS HOSTSTRIP
> >>>>>> CROSS_COMPILE
> >>>> 
> >>>> \
> >>>> 
> >>>>>> +export	HOSTCC HOSTCFLAGS HOSTLDFLAGS PEDCFLAGS HOSTSTRIP
> >>>>>> CROSS_COMPILE CCACHE \
> >>>>>> 
> >>>>>> 	AS LD CC CPP AR NM STRIP OBJCOPY OBJDUMP MAKE
> >>>>>> 
> >>>>>> export	CONFIG_SYS_TEXT_BASE PLATFORM_CPPFLAGS PLATFORM_RELFLAGS
> >>>> 
> >>>> CPPFLAGS
> >>>> 
> >>>>>> CFLAGS AFLAGS
> >>>>> 
> >>>>> Where did this patch go? I found it useful.
> >>>> 
> >>>> It needs additional fixes, try running with MAKEALL and you will see
> >>>> the problem -- the problem is you would need separate ccache for each
> >>>> MAKEALL thread.
> >>> 
> >>> I didn't use this patch but I modified config.mk as this patch did.
> >>> MAKEALL works fine for "-a powerpc". It cuts my compiling time more
> >>> than half for 660+ boards.
> >> 
> >> That is still poor, it should be much faster. If you use separate ccache
> >> for each board, then it will be _much_ more performant.
> >> 
> >> The problem is that when rebuilding all of those 680 configurations, the
> >> cached files get replaced by ones based on different board config all
> >> the time => you need to rebuild them => you loose performance.
> > 
> > I kind of get it. I have to increase my ccache size a lot (more than 2GB)
> > to get consistent cache hit. I thought that was because I was using
> > out-of-tree build when setting BUILD_NBUILDS. For the first time I run
> > MAKEALL with ccache, it was completely miss. I mean zero hit. It would
> > be nice to be able hit the cache. I was read the ccache document to
> > understand how the path is involved when calculating the hash. How do
> > you plan to make it work?
> 
> I forgot to mention, if the ccache size is at default (1GB), I don't see
> any performance improvement by using ccache. I think that's what you meant
> the cached files get replaced. I don't understand what you mean to use
> separated ccache for each board. Would it be equivalent to have a big
> cache? I was compiling with and without BUILD_NBUILDS, and my cache size
> is more than 3GB now. I could see the improvement by 2x~3x faster, but not
> more.

There is an env variable to configure separate ccache cache dir , so just by 
setting that. But then , when each build ends, you would need to clean it up 
somehow. It was mentioned in the discussion with the patch. You can try working 
on this some more and post a patch, then we can talk about further forging of 
this.

Best regards,
Marek Vasut