[PATCH v1] perf tests: Improvements to build-test performance

[PATCH v1] perf tests: Improvements to build-test performance

[Ian Rogers]

Replace hardcoded 'make' calls with '$(MAKE)' within tests/make
to ensure GNU Make jobserver file descriptors are properly inherited
by nested builds.

Additionally, remove the notorious 'unexport MAKEFLAGS' from
tools/perf/Makefile. This hack was originally added to prevent
the wrapper's internal '-j$(JOBS)' override from crashing when parent jobserver
tokens were present. Instead, use proper GNU Make conditionals to check
for '-j' or 'jobserver' strings within MAKEFLAGS. If a jobserver is
already orchestrating the build, gracefully back off and let GNU Make
manage parallelism natively.

Finally, optimize the 'out' target (which processes 'run_O' out-of-tree builds)
by stripping sequential bottlenecks like $(call clean) from isolated tmp directories,
and wrapping the target list in a parallel sub-make call.

These combined changes enable 'build-test' out-of-tree targets to
build completely concurrently without severing jobserver tokens.

Unscientifically measured the change lowered the build-test from
around 15 minutes to 10 minutes on a 28 threaded Alderlake CPU. Fixing
the jobserver issues meant the machine remained somewhat usable while
running the test.

Signed-off-by: Ian Rogers <irogers@google.com>
Assisted-by: Antigravity:gemini-3.1-pro
---
 tools/perf/Makefile   | 28 +++++++++++++++++-----------
 tools/perf/tests/make | 14 +++++++-------
 2 files changed, 24 insertions(+), 18 deletions(-)

diff --git a/tools/perf/Makefile b/tools/perf/Makefile
index 5b713837eede..45f641e24fb4 100644
--- a/tools/perf/Makefile
+++ b/tools/perf/Makefile
@@ -14,23 +14,29 @@
 .SUFFIXES:
 
 #
-# We don't want to pass along options like -j:
+# If no parallel build was requested, do a parallel build with multiple jobs,
+# based on the number of CPUs online in this system: 'make -j8' on an 8-CPU
+# system, etc.
 #
-unexport MAKEFLAGS
-
-#
-# Do a parallel build with multiple jobs, based on the number of CPUs online
-# in this system: 'make -j8' on a 8-CPU system, etc.
+# If MAKEFLAGS contains '-j' or 'jobserver', JOBS is intentionally left
+# uninitialized so the native GNU Make jobserver can seamlessly control the
+# parallel bounds of the build.
 #
 # (To override it, run 'make JOBS=1' and similar.)
 #
-ifeq ($(JOBS),)
-  JOBS := $(shell (getconf _NPROCESSORS_ONLN || grep -E -c '^processor|^CPU[0-9]' /proc/cpuinfo) 2>/dev/null)
-  ifeq ($(JOBS),0)
-    JOBS := 1
+ifeq ($(findstring -j,$(MAKEFLAGS)),)
+  ifeq ($(findstring jobserver,$(MAKEFLAGS)),)
+    ifeq ($(JOBS),)
+      JOBS := $(shell (getconf _NPROCESSORS_ONLN || grep -E -c '^processor|^CPU[0-9]' /proc/cpuinfo) 2>/dev/null)
+      ifeq ($(JOBS),0)
+        JOBS := 1
+      endif
+    endif
+    PARALLEL_OPT := -j$(JOBS)
   endif
 endif
 
+
 #
 # Only pass canonical directory names as the output directory:
 #
@@ -62,7 +68,7 @@ define print_msg
 endef
 
 define make
-  @$(MAKE) -f Makefile.perf --no-print-directory -j$(JOBS) O=$(FULL_O) $(SET_DEBUG) $@
+  @$(MAKE) -f Makefile.perf --no-print-directory $(PARALLEL_OPT) O=$(FULL_O) $(SET_DEBUG) $@
 endef
 
 #
diff --git a/tools/perf/tests/make b/tools/perf/tests/make
index d2c2f526e1db..4f14c6b72416 100644
--- a/tools/perf/tests/make
+++ b/tools/perf/tests/make
@@ -339,7 +339,6 @@ make_static:
 	rm -rf $@ $$TMP_DEST || (cat $@ ; false)
 
 $(run_O):
-	$(call clean)
 	@TMP_O=$$(mktemp -d); \
 	TMP_DEST=$$(mktemp -d); \
 	cmd="cd $(PERF) && $(MAKE_F) $($(patsubst %_O,%,$@)) $(PARALLEL_OPT) O=$$TMP_O DESTDIR=$$TMP_DEST"; \
@@ -363,18 +362,18 @@ endif
 make_kernelsrc:
 	@echo "- make -C <kernelsrc> $(PARALLEL_OPT) $(K_O_OPT) tools/perf"
 	$(call clean); \
-	(make -C ../.. $(PARALLEL_OPT) $(K_O_OPT) tools/perf) > $@ 2>&1 && \
+	($(MAKE) -C ../.. $(PARALLEL_OPT) $(K_O_OPT) tools/perf) > $@ 2>&1 && \
 	test -x $(KERNEL_O)/tools/perf/perf && rm -f $@ || (cat $@ ; false)
 
 make_kernelsrc_tools:
 	@echo "- make -C <kernelsrc>/tools $(PARALLEL_OPT) $(K_O_OPT) perf"
 	$(call clean); \
-	(make -C ../../tools $(PARALLEL_OPT) $(K_O_OPT) perf) > $@ 2>&1 && \
+	($(MAKE) -C ../../tools $(PARALLEL_OPT) $(K_O_OPT) perf) > $@ 2>&1 && \
 	test -x $(KERNEL_O)/tools/perf/perf && rm -f $@ || (cat $@ ; false)
 
 make_libperf:
 	@echo "- make -C lib";
-	make -C lib clean >$@ 2>&1; make -C lib >>$@ 2>&1 && rm $@
+	$(MAKE) -C lib clean >$@ 2>&1; $(MAKE) -C lib >>$@ 2>&1 && rm $@
 
 FEATURES_DUMP_FILE := $(FULL_O)/BUILD_TEST_FEATURE_DUMP
 FEATURES_DUMP_FILE_STATIC := $(FULL_O)/BUILD_TEST_FEATURE_DUMP_STATIC
@@ -383,20 +382,21 @@ all: $(run) $(run_O) tarpkg make_kernelsrc make_kernelsrc_tools
 	@echo OK
 	@rm -f $(FEATURES_DUMP_FILE) $(FEATURES_DUMP_FILE_STATIC)
 
-out: $(run_O)
+out: $(FEATURES_DUMP_FILE) $(FEATURES_DUMP_FILE_STATIC)
+	@$(MAKE) -f tests/make $(run_O) PARALLEL_OPT= -j$(cores)
 	@echo OK
 	@rm -f $(FEATURES_DUMP_FILE) $(FEATURES_DUMP_FILE_STATIC)
 
 ifeq ($(REUSE_FEATURES_DUMP),1)
 $(FEATURES_DUMP_FILE):
 	$(call clean)
-	@cmd="cd $(PERF) && make FEATURE_DUMP_COPY=$@ $(O_OPT) feature-dump"; \
+	@cmd="cd $(PERF) && $(MAKE) FEATURE_DUMP_COPY=$@ $(O_OPT) feature-dump"; \
 	echo "- $@: $$cmd" && echo $$cmd && \
 	( eval $$cmd ) > /dev/null 2>&1
 
 $(FEATURES_DUMP_FILE_STATIC):
 	$(call clean)
-	@cmd="cd $(PERF) && make FEATURE_DUMP_COPY=$@ $(O_OPT) LDFLAGS='-static' feature-dump"; \
+	@cmd="cd $(PERF) && $(MAKE) FEATURE_DUMP_COPY=$@ $(O_OPT) LDFLAGS='-static' feature-dump"; \
 	echo "- $@: $$cmd" && echo $$cmd && \
 	( eval $$cmd ) > /dev/null 2>&1
 
-- 
2.55.0.966.g6673acef38-goog

Re: [PATCH v1] perf tests: Improvements to build-test performance

[sashiko-bot]

Thank you for your contribution! Sashiko AI review found 2 potential issue(s) to consider:
- [High] The `out` target explicitly passes `-j$(cores)` to a sub-make, breaking GNU Make's native jobserver inheritance and triggering an unbounded fork bomb if `cores` is undefined.
- [Medium] Removing `$(call clean)` from `$(run_O)` causes out-of-tree builds to execute on a dirty source tree when run sequentially after in-tree builds.
--

commit 169a507e0cde997201a5b5a2dfdbe4652f1a9fa0
Author: Ian Rogers <irogers@google.com>

perf tests: Improvements to build-test performance

This commit aims to improve build-test performance by using $(MAKE) to ensure
GNU Make jobserver file descriptors are inherited by nested builds. It removes
sequential bottlenecks like $(call clean) from isolated tmp directories and
wraps the out target list in a parallel sub-make call.

> diff --git a/tools/perf/tests/make b/tools/perf/tests/make
> index d2c2f526e1db0..4f14c6b72416a 100644
> --- a/tools/perf/tests/make
> +++ b/tools/perf/tests/make
> @@ -339,7 +339,6 @@ make_static:
>  	rm -rf $@ $$TMP_DEST || (cat $@ ; false)
>  
>  $(run_O):
> -	$(call clean)

[Severity: Medium]
Does removing this clean step cause out-of-tree builds to execute on a dirty
source tree when run sequentially?

When the default all target is executed:

all: $(run) $(run_O) tarpkg make_kernelsrc make_kernelsrc_tools

The $(run) in-tree builds execute first and leave the source tree dirty.
Since $(run_O) no longer calls $(call clean) before starting, it appears
the first out-of-tree build begins on that dirty source tree, breaking
build isolation.

>  	@TMP_O=$$(mktemp -d); \
>  	TMP_DEST=$$(mktemp -d); \
>  	cmd="cd $(PERF) && $(MAKE_F) $($(patsubst %_O,%,$@)) $(PARALLEL_OPT) O=$$TMP_O DESTDIR=$$TMP_DEST"; \

[ ... ]

> @@ -383,20 +382,21 @@ all: $(run) $(run_O) tarpkg make_kernelsrc make_kernelsrc_tools
>  	@echo OK
>  	@rm -f $(FEATURES_DUMP_FILE) $(FEATURES_DUMP_FILE_STATIC)
>  
> -out: $(run_O)
> +out: $(FEATURES_DUMP_FILE) $(FEATURES_DUMP_FILE_STATIC)
> +	@$(MAKE) -f tests/make $(run_O) PARALLEL_OPT= -j$(cores)

[Severity: High]
Does passing -j$(cores) here break native jobserver inheritance and risk an
unbounded fork bomb?

If a developer runs the out target directly without setting cores, the
-j$(cores) flag expands to -j without an integer. This instructs GNU Make
to spawn unlimited jobs, which is then inherited by all $(run_O) sub-makes.

Additionally, even when cores is defined, passing it explicitly to $(MAKE)
overrides any --jobserver-auth tokens passed from a parent make, breaking
the jobserver inheritance this patch aims to fix.

>  	@echo OK
>  	@rm -f $(FEATURES_DUMP_FILE) $(FEATURES_DUMP_FILE_STATIC)

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260902153135.2067365-1-irogers@google.com?part=1

[PATCH v2] perf tests: Improvements to build-test performance

[Ian Rogers]

Replace hardcoded 'make' calls with '$(MAKE)' within tests/make to
ensure GNU Make jobserver file descriptors are properly inherited by
nested builds.

Additionally, remove the 'unexport MAKEFLAGS' from
tools/perf/Makefile. This hack was originally added to prevent the
wrapper's internal '-j$(JOBS)' override from crashing when parent
jobserver tokens were present. Instead, use proper GNU Make
conditionals to check for '-j' or 'jobserver' strings within
MAKEFLAGS. If a jobserver is already orchestrating the build,
gracefully back off and let GNU Make manage parallelism natively.

Finally, optimize the 'out' target (which processes 'run_O'
out-of-tree builds) by stripping sequential bottlenecks like $(call
clean) from isolated tmp directories, and wrapping the target list in
a parallel sub-make call.

These combined changes enable 'build-test' out-of-tree targets to
build completely concurrently without severing jobserver tokens.

Unscientifically measured the change lowered the build-test from
around 15 minutes to 10 minutes on a 28 threaded Alderlake CPU. Fixing
the jobserver issues meant the machine remained somewhat usable while
running the test.

Signed-off-by: Ian Rogers <irogers@google.com>
Assisted-by: Antigravity:gemini-3.1-pro
---
v2:
 - Re-structured build-test array in tools/perf/Makefile into explicit
   sequential $(MAKE) passes. This prevents in-tree targets (make_static,
   etc.) from racing to directory corruption when exposed to native
   jobservers.
 - Added '+' prefix to recipe modifiers in tests/make to prevent jobserver
   FDs from being stripped before sub-shell evaluation.
 - Replaced hardcoded -j$(cores) limits in the 'out' sub-make step with
   dynamic jobserver boundary detection to prevent fork-bomb override
   collisions.
 - Restored missing $(call clean) steps via O_CLEAN conditionals to prevent
   in-tree polluted runs from breaking out-of-tree sequences.
 - Removed unconditionally appended $(FEATURES_DUMP_FILE) target restrictions
   from 'out' that threw "No rule to make target" errors on unhandled tests.
 - Fixed 'test_dest_files' to check [ ! -f ] instead of [ ! -x ], removing
   long-standing ghost warnings for non-executable mode-644 targets
   like etc/bash_completion.d/perf.
 - Fixed cosmetic string formatting bugs in GNU Make's print_msg banner
   output.
---
 tools/perf/Makefile   | 35 ++++++++++++++++++++++-------------
 tools/perf/tests/make | 42 ++++++++++++++++++++++++------------------
 2 files changed, 46 insertions(+), 31 deletions(-)

diff --git a/tools/perf/Makefile b/tools/perf/Makefile
index 5b713837eede..2cbf4cb5f093 100644
--- a/tools/perf/Makefile
+++ b/tools/perf/Makefile
@@ -14,23 +14,29 @@
 .SUFFIXES:
 
 #
-# We don't want to pass along options like -j:
+# If no parallel build was requested, do a parallel build with multiple jobs,
+# based on the number of CPUs online in this system: 'make -j8' on an 8-CPU
+# system, etc.
 #
-unexport MAKEFLAGS
-
-#
-# Do a parallel build with multiple jobs, based on the number of CPUs online
-# in this system: 'make -j8' on a 8-CPU system, etc.
+# If MAKEFLAGS contains '-j' or 'jobserver', JOBS is intentionally left
+# uninitialized so the native GNU Make jobserver can seamlessly control the
+# parallel bounds of the build.
 #
 # (To override it, run 'make JOBS=1' and similar.)
 #
-ifeq ($(JOBS),)
-  JOBS := $(shell (getconf _NPROCESSORS_ONLN || grep -E -c '^processor|^CPU[0-9]' /proc/cpuinfo) 2>/dev/null)
-  ifeq ($(JOBS),0)
-    JOBS := 1
+ifeq ($(findstring -j,$(MAKEFLAGS)),)
+  ifeq ($(findstring jobserver,$(MAKEFLAGS)),)
+    ifeq ($(JOBS),)
+      JOBS := $(shell (getconf _NPROCESSORS_ONLN || grep -E -c '^processor|^CPU[0-9]' /proc/cpuinfo) 2>/dev/null)
+      ifeq ($(JOBS),0)
+        JOBS := 1
+      endif
+    endif
+    PARALLEL_OPT := -j$(JOBS)
   endif
 endif
 
+
 #
 # Only pass canonical directory names as the output directory:
 #
@@ -58,11 +64,11 @@ else
 endif
 
 define print_msg
-  @printf '  BUILD:   Doing '\''make \033[33m-j'$(JOBS)'\033[m'\'' $(BUILD_TYPE) build\n'
+  @printf '  BUILD:   Doing '\''make\033[33m%s\033[m'\'' $(BUILD_TYPE) build\n' "$(if $(JOBS), -j$(JOBS),)"
 endef
 
 define make
-  @$(MAKE) -f Makefile.perf --no-print-directory -j$(JOBS) O=$(FULL_O) $(SET_DEBUG) $@
+  @$(MAKE) -f Makefile.perf --no-print-directory $(PARALLEL_OPT) O=$(FULL_O) $(SET_DEBUG) $@
 endef
 
 #
@@ -106,7 +112,10 @@ clean:
 # make -C tools/perf -f tests/make
 #
 build-test:
-	@$(MAKE) SHUF=1 -f tests/make REUSE_FEATURES_DUMP=1 MK=Makefile SET_PARALLEL=1 --no-print-directory tarpkg make_static make_with_gtk2 out
+	@$(MAKE) SHUF=1 -f tests/make REUSE_FEATURES_DUMP=1 MK=Makefile SET_PARALLEL=1 --no-print-directory tarpkg
+	@$(MAKE) SHUF=1 -f tests/make REUSE_FEATURES_DUMP=1 MK=Makefile SET_PARALLEL=1 --no-print-directory make_static
+	@$(MAKE) SHUF=1 -f tests/make REUSE_FEATURES_DUMP=1 MK=Makefile SET_PARALLEL=1 --no-print-directory make_with_gtk2
+	@$(MAKE) SHUF=1 -f tests/make REUSE_FEATURES_DUMP=1 MK=Makefile SET_PARALLEL=1 --no-print-directory out
 
 build-test-tarball:
 	@$(MAKE) -f tests/make REUSE_FEATURES_DUMP=1 MK=Makefile SET_PARALLEL=1 --no-print-directory out
diff --git a/tools/perf/tests/make b/tools/perf/tests/make
index d2c2f526e1db..d1d99f5a85ae 100644
--- a/tools/perf/tests/make
+++ b/tools/perf/tests/make
@@ -28,15 +28,17 @@ endif
 
 PARALLEL_OPT=
 ifeq ($(SET_PARALLEL),1)
-  ifeq ($(JOBS),)
-    cores := $(shell (getconf _NPROCESSORS_ONLN || grep -E -c '^processor|^CPU[0-9]' /proc/cpuinfo) 2>/dev/null)
-    ifeq ($(cores),0)
-      cores := 1
+  ifeq ($(findstring jobserver,$(MAKEFLAGS))$(findstring -j,$(MAKEFLAGS)),)
+    ifeq ($(JOBS),)
+      cores := $(shell (getconf _NPROCESSORS_ONLN || grep -E -c '^processor|^CPU[0-9]' /proc/cpuinfo) 2>/dev/null)
+      ifeq ($(cores),0)
+        cores := 1
+      endif
+    else
+      cores=$(JOBS)
     endif
-  else
-    cores=$(JOBS)
+    PARALLEL_OPT="-j$(cores)"
   endif
-  PARALLEL_OPT="-j$(cores)"
 endif
 
 # As per kernel Makefile, avoid funny character set dependencies
@@ -230,7 +232,7 @@ test_make_util_pmu_bison_o := test -f $(PERF_O)/util/pmu-bison.o
 
 define test_dest_files
   for file in $(1); do				\
-    if [ ! -x $$TMP_DEST/$$file ]; then		\
+    if [ ! -f $$TMP_DEST/$$file ]; then		\
       echo "  failed to find: $$file";		\
     fi						\
   done
@@ -310,7 +312,7 @@ clean := @(cd $(PERF); $(MAKE_F) -s $(O_OPT) clean >/dev/null && $(MAKE) -s $(O_
 
 $(run):
 	$(call clean)
-	@TMP_DEST=$$(mktemp -d); \
+	+@TMP_DEST=$$(mktemp -d); \
 	cmd="cd $(PERF) && $(MAKE_F) $($@) $(PARALLEL_OPT) $(O_OPT) DESTDIR=$$TMP_DEST"; \
 	printf "%*.*s: %s\n" $(max_width) $(max_width) "$@" "$$cmd" && echo $$cmd > $@ && \
 	( eval $$cmd ) >> $@ 2>&1; \
@@ -320,7 +322,7 @@ $(run):
 
 make_with_gtk2:
 	$(call clean)
-	@TMP_DEST=$$(mktemp -d); \
+	+@TMP_DEST=$$(mktemp -d); \
 	cmd="cd $(PERF) && $(MAKE_F) $($@) $(PARALLEL_OPT) $(O_OPT) DESTDIR=$$TMP_DEST"; \
 	printf "%*.*s: %s\n" $(max_width) $(max_width) "$@" "$$cmd" && echo $$cmd > $@ && \
 	( eval $$cmd ) >> $@ 2>&1; \
@@ -330,7 +332,7 @@ make_with_gtk2:
 
 make_static:
 	$(call clean)
-	@TMP_DEST=$$(mktemp -d); \
+	+@TMP_DEST=$$(mktemp -d); \
 	cmd="cd $(PERF) && $(MAKE_F) $($@) $(PARALLEL_OPT) $(O_OPT) DESTDIR=$$TMP_DEST"; \
 	printf "%*.*s: %s\n" $(max_width) $(max_width) "$@" "$$cmd" && echo $$cmd > $@ && \
 	( eval $$cmd ) >> $@ 2>&1; \
@@ -339,8 +341,10 @@ make_static:
 	rm -rf $@ $$TMP_DEST || (cat $@ ; false)
 
 $(run_O):
+ifneq ($(O_CLEAN),0)
 	$(call clean)
-	@TMP_O=$$(mktemp -d); \
+endif
+	+@TMP_O=$$(mktemp -d); \
 	TMP_DEST=$$(mktemp -d); \
 	cmd="cd $(PERF) && $(MAKE_F) $($(patsubst %_O,%,$@)) $(PARALLEL_OPT) O=$$TMP_O DESTDIR=$$TMP_DEST"; \
 	printf "%*.*s: %s\n" $(max_width) $(max_width) "$@" "$$cmd" && echo $$cmd > $@ && \
@@ -363,18 +367,18 @@ endif
 make_kernelsrc:
 	@echo "- make -C <kernelsrc> $(PARALLEL_OPT) $(K_O_OPT) tools/perf"
 	$(call clean); \
-	(make -C ../.. $(PARALLEL_OPT) $(K_O_OPT) tools/perf) > $@ 2>&1 && \
+	($(MAKE) -C ../.. $(PARALLEL_OPT) $(K_O_OPT) tools/perf) > $@ 2>&1 && \
 	test -x $(KERNEL_O)/tools/perf/perf && rm -f $@ || (cat $@ ; false)
 
 make_kernelsrc_tools:
 	@echo "- make -C <kernelsrc>/tools $(PARALLEL_OPT) $(K_O_OPT) perf"
 	$(call clean); \
-	(make -C ../../tools $(PARALLEL_OPT) $(K_O_OPT) perf) > $@ 2>&1 && \
+	($(MAKE) -C ../../tools $(PARALLEL_OPT) $(K_O_OPT) perf) > $@ 2>&1 && \
 	test -x $(KERNEL_O)/tools/perf/perf && rm -f $@ || (cat $@ ; false)
 
 make_libperf:
 	@echo "- make -C lib";
-	make -C lib clean >$@ 2>&1; make -C lib >>$@ 2>&1 && rm $@
+	$(MAKE) -C lib clean >$@ 2>&1; $(MAKE) -C lib >>$@ 2>&1 && rm $@
 
 FEATURES_DUMP_FILE := $(FULL_O)/BUILD_TEST_FEATURE_DUMP
 FEATURES_DUMP_FILE_STATIC := $(FULL_O)/BUILD_TEST_FEATURE_DUMP_STATIC
@@ -383,20 +387,22 @@ all: $(run) $(run_O) tarpkg make_kernelsrc make_kernelsrc_tools
 	@echo OK
 	@rm -f $(FEATURES_DUMP_FILE) $(FEATURES_DUMP_FILE_STATIC)
 
-out: $(run_O)
+out:
+	$(call clean)
+	@$(MAKE) -f tests/make $(run_O) PARALLEL_OPT= O_CLEAN=0 $(if $(findstring jobserver,$(MAKEFLAGS))$(findstring -j,$(MAKEFLAGS)),,$(if $(cores),-j$(cores)))
 	@echo OK
 	@rm -f $(FEATURES_DUMP_FILE) $(FEATURES_DUMP_FILE_STATIC)
 
 ifeq ($(REUSE_FEATURES_DUMP),1)
 $(FEATURES_DUMP_FILE):
 	$(call clean)
-	@cmd="cd $(PERF) && make FEATURE_DUMP_COPY=$@ $(O_OPT) feature-dump"; \
+	@cmd="cd $(PERF) && $(MAKE) FEATURE_DUMP_COPY=$@ $(O_OPT) feature-dump"; \
 	echo "- $@: $$cmd" && echo $$cmd && \
 	( eval $$cmd ) > /dev/null 2>&1
 
 $(FEATURES_DUMP_FILE_STATIC):
 	$(call clean)
-	@cmd="cd $(PERF) && make FEATURE_DUMP_COPY=$@ $(O_OPT) LDFLAGS='-static' feature-dump"; \
+	@cmd="cd $(PERF) && $(MAKE) FEATURE_DUMP_COPY=$@ $(O_OPT) LDFLAGS='-static' feature-dump"; \
 	echo "- $@: $$cmd" && echo $$cmd && \
 	( eval $$cmd ) > /dev/null 2>&1
 
-- 
2.55.0.979.g7e5102b832-goog

Re: [PATCH v2] perf tests: Improvements to build-test performance

[sashiko-bot]

> Replace hardcoded 'make' calls with '$(MAKE)' within tests/make to
> ensure GNU Make jobserver file descriptors are properly inherited by
> nested builds.
> 
> Additionally, remove the 'unexport MAKEFLAGS' from
> tools/perf/Makefile. This hack was originally added to prevent the
> wrapper's internal '-j$(JOBS)' override from crashing when parent
> jobserver tokens were present. Instead, use proper GNU Make
> conditionals to check for '-j' or 'jobserver' strings within
> MAKEFLAGS. If a jobserver is already orchestrating the build,
> gracefully back off and let GNU Make manage parallelism natively.
> 
> Finally, optimize the 'out' target (which processes 'run_O'
> out-of-tree builds) by stripping sequential bottlenecks like $(call
> clean) from isolated tmp directories, and wrapping the target list in
> a parallel sub-make call.
> 
> These combined changes enable 'build-test' out-of-tree targets to
> build completely concurrently without severing jobserver tokens.
> 
> Unscientifically measured the change lowered the build-test from
> around 15 minutes to 10 minutes on a 28 threaded Alderlake CPU. Fixing
> the jobserver issues meant the machine remained somewhat usable while
> running the test.
> 
> Signed-off-by: Ian Rogers <irogers@google.com>

Sashiko has reviewed this patch and found no issues. It looks great!

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260903045603.3611902-1-irogers@google.com?part=1