From e17c400ae194945eef9d9cae38a321c92c1986fb Mon Sep 17 00:00:00 2001
From: Masahiro Yamada <yamada.masahiro@socionext.com>
Date: Fri, 13 Oct 2017 20:25:29 +0900
Subject: [PATCH] kbuild: shrink .cache.mk when it exceeds 1000 lines

The cache files are only cleaned away by "make clean".  If you continue
incremental builds, the cache files will grow up little by little.
It is not a big deal in general use cases because compiler flags do not
change quite often.

However, if you do build-test for various architectures, compilers, and
kernel configurations, you will end up with huge cache files soon.

When the cache file exceeds 1000 lines, shrink it down to 500 by "tail".
The Least Recently Added lines are cut. (not Least Recently Used)
I hope it will work well enough.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
---
 scripts/Kbuild.include | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/scripts/Kbuild.include b/scripts/Kbuild.include
index dfadb1c94368f..064f477dfdca0 100644
--- a/scripts/Kbuild.include
+++ b/scripts/Kbuild.include
@@ -105,6 +105,12 @@ endif
 $(make-cache): ;
 -include $(make-cache)
 
+# If cache exceeds 1000 lines, shrink it down to 500.
+ifneq ($(word 1000,$(filter __cached_%, $(.VARIABLES))),)
+$(shell tail -n 500 $(make-cache) > $(make-cache).tmp; \
+	mv $(make-cache).tmp $(make-cache))
+endif
+
 # Usage: $(call __sanitize-opt,Hello=Hola$(comma)Goodbye Adios)
 #
 # Convert all '$', ')', '(', '\', '=', ' ', ',', ':' to '_'
-- 
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