[PATCH v2] backports: significantly speed up build

[PATCH v2] backports: significantly speed up build

[Johannes Berg]

From: Johannes Berg <johannes.berg@intel.com>

When building with /bin/sh -> bash, things are SUPER slow (at least
for me), because bash takes a LOOONG time to look at the environment
variables (and we typically have around 6k), adding over a second to
each bash invocation for me.

The reason we export them is that we need them in all of the sub-
makes, and those only read auto.conf, which we can't change.

Work around this by overriding 'make' itself, and using --eval to
read *our* .config file into each make that gets called. This way,
the variables are present in all make invocations in the same way
as they would be through the environment, but don't get passed to
shell invocations.

If --eval is not supported, keep doing what we did before.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
---
 backport/Makefile.build | 7 +++++++
 backport/scripts/make   | 4 ++++
 2 files changed, 11 insertions(+)
 create mode 100755 backport/scripts/make

diff --git a/backport/Makefile.build b/backport/Makefile.build
index a848b37ed64b..9c272b2ddf62 100644
--- a/backport/Makefile.build
+++ b/backport/Makefile.build
@@ -1,4 +1,11 @@
+# detect if make supports --eval
+_EVAL := $(shell make --eval "test:" -f /dev/null test >/dev/null 2>&1 && echo YES || echo NO)
+ifeq ($(_EVAL),YES)
+MAKE=$(BACKPORT_DIR)/scripts/make
+else
 -include .config
+endif
+
 export
 
 .PHONY: modules
diff --git a/backport/scripts/make b/backport/scripts/make
new file mode 100755
index 000000000000..cff7d0031478
--- /dev/null
+++ b/backport/scripts/make
@@ -0,0 +1,4 @@
+#!/bin/sh
+# SPDX-License-Identifier: GPL-2.0
+
+exec make --eval '-include $(BACKPORT_DIR)/.config' "$@"
-- 
2.23.0

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Re: [PATCH v2] backports: significantly speed up build

[Johannes Berg]

On Tue, 2019-12-03 at 17:15 +0100, Johannes Berg wrote:
> 
> If --eval is not supported, keep doing what we did before.

It's a bit disconcerting that we have systems that run make 3.81 or
older, but apparently that's what happened?! That was released over 9
years ago, and --eval was added to the code base 10 years ago ...

johannes

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Re: [PATCH v2] backports: significantly speed up build

[Hauke Mehrtens]

On 12/3/19 5:28 PM, Johannes Berg wrote:
> On Tue, 2019-12-03 at 17:15 +0100, Johannes Berg wrote:
>>
>> If --eval is not supported, keep doing what we did before.
> 
> It's a bit disconcerting that we have systems that run make 3.81 or
> older, but apparently that's what happened?! That was released over 9
> years ago, and --eval was added to the code base 10 years ago ...
> 
> johannes

Hi Johannes,

This looks good, but I am not an bash expert.

Even RedHat 7.7 uses make 3.82, so I do not care about older versions
any more.

Hauke
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Re: [PATCH v2] backports: significantly speed up build

[Johannes Berg]

On Mon, 2019-12-23 at 19:51 +0100, Hauke Mehrtens wrote:
> On 12/3/19 5:28 PM, Johannes Berg wrote:
> > On Tue, 2019-12-03 at 17:15 +0100, Johannes Berg wrote:
> > > If --eval is not supported, keep doing what we did before.
> > 
> > It's a bit disconcerting that we have systems that run make 3.81 or
> > older, but apparently that's what happened?! That was released over 9
> > years ago, and --eval was added to the code base 10 years ago ...
> > 
> > johannes

> This looks good, but I am not an bash expert.

Neither am I! I just noticed the speed problem :-)

Really though, this change isn't much related to bash, right? It just
passes the variables to the sub-make in a different way.

> Even RedHat 7.7 uses make 3.82, so I do not care about older versions
> any more.

Cool. We had some older ones around in our infrastructure ... working to
get rid of them :)

johannes

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