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From: Masahiro Yamada <masahiroy@kernel.org>
To: linux-kbuild@vger.kernel.org
Cc: linux-s390@vger.kernel.org, Nicolas Schier <nicolas@fjasle.eu>,
	Peter Zijlstra <peterz@infradead.org>,
	Masahiro Yamada <masahiroy@kernel.org>,
	Nick Desaulniers <ndesaulniers@google.com>,
	linux-kernel@vger.kernel.org,
	Nathan Chancellor <nathan@kernel.org>,
	clang-built-linux@googlegroups.com,
	Sami Tolvanen <samitolvanen@google.com>,
	linuxppc-dev@lists.ozlabs.org, Ard Biesheuvel <ardb@kernel.org>,
	linux-modules@vger.kernel.org
Subject: [PATCH v4 11/14] kbuild: make built-in.a rule robust against too long argument error
Date: Mon,  9 May 2022 04:06:28 +0900	[thread overview]
Message-ID: <20220508190631.2386038-12-masahiroy@kernel.org> (raw)
In-Reply-To: <20220508190631.2386038-1-masahiroy@kernel.org>

Kbuild runs at the top of objtree instead of changing the working
directory to subdirectories. I think this design is nice overall but
some commands have a scalability issue.

The build command of built-in.a is one of them whose length scales with:

    O(D * N)

Here, D is the length of the directory path (i.e. $(obj)/ prefix),
N is the number of objects in the Makefile, O() is the big O notation.

The deeper directory the Makefile directory is located, the more easily
it will hit the too long argument error.

We can make it better. Trim the $(obj)/ by Make's builtin function, and
restore it by a shell command (sed).

With this, the command length scales with:

    O(D + N)

In-tree modules still have some room to the limit (ARG_MAX=2097152),
but this is more future-proof for big modules in a deep directory.

For example, you can build i915 as builtin (CONFIG_DRM_I915=y) and
compare drivers/gpu/drm/i915/.built-in.a.cmd with/without this commit.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nicolas Schier <nicolas@fjasle.eu>
Tested-by: Nathan Chancellor <nathan@kernel.org>
---

(no changes since v2)

Changes in v2:
  - New patch

 scripts/Makefile.build | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/scripts/Makefile.build b/scripts/Makefile.build
index c2a173b3fd60..8f1a355df7aa 100644
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -374,7 +374,10 @@ $(subdir-modorder): $(obj)/%/modules.order: $(obj)/% ;
 #
 
 quiet_cmd_ar_builtin = AR      $@
-      cmd_ar_builtin = rm -f $@; $(AR) cDPrST $@ $(real-prereqs)
+      cmd_ar_builtin = rm -f $@; \
+		echo $(patsubst $(obj)/%,%,$(real-prereqs)) | \
+		sed -E 's:([^ ]+):$(obj)/\1:g' | \
+		xargs $(AR) cDPrST $@
 
 $(obj)/built-in.a: $(real-obj-y) FORCE
 	$(call if_changed,ar_builtin)
-- 
2.32.0


WARNING: multiple messages have this Message-ID
From: Masahiro Yamada <masahiroy@kernel.org>
To: linux-kbuild@vger.kernel.org
Cc: linux-kernel@vger.kernel.org,
	Nathan Chancellor <nathan@kernel.org>,
	Nick Desaulniers <ndesaulniers@google.com>,
	Nicolas Schier <nicolas@fjasle.eu>,
	Peter Zijlstra <peterz@infradead.org>,
	linux-modules@vger.kernel.org, linux-s390@vger.kernel.org,
	linuxppc-dev@lists.ozlabs.org,
	clang-built-linux@googlegroups.com,
	Ard Biesheuvel <ardb@kernel.org>,
	Sami Tolvanen <samitolvanen@google.com>,
	Masahiro Yamada <masahiroy@kernel.org>
Subject: [PATCH v4 11/14] kbuild: make built-in.a rule robust against too long argument error
Date: Mon,  9 May 2022 04:06:28 +0900	[thread overview]
Message-ID: <20220508190631.2386038-12-masahiroy@kernel.org> (raw)
In-Reply-To: <20220508190631.2386038-1-masahiroy@kernel.org>

Kbuild runs at the top of objtree instead of changing the working
directory to subdirectories. I think this design is nice overall but
some commands have a scalability issue.

The build command of built-in.a is one of them whose length scales with:

    O(D * N)

Here, D is the length of the directory path (i.e. $(obj)/ prefix),
N is the number of objects in the Makefile, O() is the big O notation.

The deeper directory the Makefile directory is located, the more easily
it will hit the too long argument error.

We can make it better. Trim the $(obj)/ by Make's builtin function, and
restore it by a shell command (sed).

With this, the command length scales with:

    O(D + N)

In-tree modules still have some room to the limit (ARG_MAX=2097152),
but this is more future-proof for big modules in a deep directory.

For example, you can build i915 as builtin (CONFIG_DRM_I915=y) and
compare drivers/gpu/drm/i915/.built-in.a.cmd with/without this commit.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nicolas Schier <nicolas@fjasle.eu>
Tested-by: Nathan Chancellor <nathan@kernel.org>
---

(no changes since v2)

Changes in v2:
  - New patch

 scripts/Makefile.build | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/scripts/Makefile.build b/scripts/Makefile.build
index c2a173b3fd60..8f1a355df7aa 100644
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -374,7 +374,10 @@ $(subdir-modorder): $(obj)/%/modules.order: $(obj)/% ;
 #
 
 quiet_cmd_ar_builtin = AR      $@
-      cmd_ar_builtin = rm -f $@; $(AR) cDPrST $@ $(real-prereqs)
+      cmd_ar_builtin = rm -f $@; \
+		echo $(patsubst $(obj)/%,%,$(real-prereqs)) | \
+		sed -E 's:([^ ]+):$(obj)/\1:g' | \
+		xargs $(AR) cDPrST $@
 
 $(obj)/built-in.a: $(real-obj-y) FORCE
 	$(call if_changed,ar_builtin)
-- 
2.32.0


  parent reply	other threads:[~2022-05-08 19:16 UTC|newest]

Thread overview: 68+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-05-08 19:06 [PATCH v4 00/14] kbuild: yet another series of cleanups (modpost, LTO, MODULE_REL_CRCS, export.h) Masahiro Yamada
2022-05-08 19:06 ` Masahiro Yamada
2022-05-08 19:06 ` [PATCH v4 01/14] modpost: remove left-over cross_compile declaration Masahiro Yamada
2022-05-08 19:06   ` Masahiro Yamada
2022-05-09 17:08   ` Nick Desaulniers
2022-05-09 17:08     ` Nick Desaulniers
2022-05-12  4:35   ` Masahiro Yamada
2022-05-12  4:35     ` Masahiro Yamada
2022-05-08 19:06 ` [PATCH v4 02/14] modpost: change the license of EXPORT_SYMBOL to bool type Masahiro Yamada
2022-05-08 19:06   ` Masahiro Yamada
2022-05-12  4:36   ` Masahiro Yamada
2022-05-12  4:36     ` Masahiro Yamada
2022-05-08 19:06 ` [PATCH v4 03/14] modpost: split the section mismatch checks into section-check.c Masahiro Yamada
2022-05-08 19:06   ` Masahiro Yamada
2022-05-09 17:19   ` Nick Desaulniers
2022-05-09 17:19     ` Nick Desaulniers
2022-05-10  6:55     ` Masahiro Yamada
2022-05-10  6:55       ` Masahiro Yamada
2022-05-11 18:47       ` Nick Desaulniers
2022-05-11 18:47         ` Nick Desaulniers
2022-05-11 19:27         ` Masahiro Yamada
2022-05-11 19:27           ` Masahiro Yamada
2022-05-11 19:51           ` Jeff Johnson
2022-05-11 19:51             ` Jeff Johnson
2022-05-11 20:01             ` Nick Desaulniers
2022-05-11 20:01               ` Nick Desaulniers
2022-05-08 19:06 ` [PATCH v4 04/14] modpost: add sym_find_with_module() helper Masahiro Yamada
2022-05-08 19:06   ` Masahiro Yamada
2022-05-08 19:06 ` [PATCH v4 05/14] modpost: extract symbol versions from *.cmd files Masahiro Yamada
2022-05-08 19:06   ` Masahiro Yamada
2022-05-09 21:52   ` Sami Tolvanen
2022-05-09 21:52     ` Sami Tolvanen
2022-05-08 19:06 ` [PATCH v4 06/14] kbuild: link symbol CRCs at final link, removing CONFIG_MODULE_REL_CRCS Masahiro Yamada
2022-05-08 19:06   ` Masahiro Yamada
2022-05-09 17:50   ` Nick Desaulniers
2022-05-09 17:50     ` Nick Desaulniers
2022-05-10 13:03     ` Masahiro Yamada
2022-05-10 13:03       ` Masahiro Yamada
2022-05-08 19:06 ` [PATCH v4 07/14] kbuild: stop merging *.symversions Masahiro Yamada
2022-05-08 19:06   ` Masahiro Yamada
2022-05-08 19:06 ` [PATCH v4 08/14] genksyms: adjust the output format to modpost Masahiro Yamada
2022-05-08 19:06   ` Masahiro Yamada
2022-05-08 19:06 ` [PATCH v4 09/14] kbuild: do not create *.prelink.o for Clang LTO or IBT Masahiro Yamada
2022-05-08 19:06   ` Masahiro Yamada
2022-05-09 23:13   ` Sami Tolvanen
2022-05-09 23:13     ` Sami Tolvanen
2022-05-08 19:06 ` [PATCH v4 10/14] kbuild: check static EXPORT_SYMBOL* by script instead of modpost Masahiro Yamada
2022-05-08 19:06   ` Masahiro Yamada
2022-05-09 18:05   ` Nick Desaulniers
2022-05-09 18:05     ` Nick Desaulniers
2022-05-10 13:53     ` Masahiro Yamada
2022-05-10 13:53       ` Masahiro Yamada
2022-05-08 19:06 ` Masahiro Yamada [this message]
2022-05-08 19:06   ` [PATCH v4 11/14] kbuild: make built-in.a rule robust against too long argument error Masahiro Yamada
2022-05-08 19:06 ` [PATCH v4 12/14] kbuild: make *.mod " Masahiro Yamada
2022-05-08 19:06   ` Masahiro Yamada
2022-05-08 19:06 ` [PATCH v4 13/14] kbuild: add cmd_and_savecmd macro Masahiro Yamada
2022-05-08 19:06   ` Masahiro Yamada
2022-05-08 19:06 ` [PATCH v4 14/14] kbuild: rebuild multi-object modules when objtool is updated Masahiro Yamada
2022-05-08 19:06   ` Masahiro Yamada
2022-05-09  4:24 ` [PATCH v4 00/14] kbuild: yet another series of cleanups (modpost, LTO, MODULE_REL_CRCS, export.h) Masahiro Yamada
2022-05-09  4:24   ` Masahiro Yamada
2022-05-09 22:13   ` Nathan Chancellor
2022-05-09 22:13     ` Nathan Chancellor
2022-05-10  6:55     ` Masahiro Yamada
2022-05-10  6:55       ` Masahiro Yamada
2022-05-09 22:19   ` Nathan Chancellor
2022-05-09 22:19     ` Nathan Chancellor

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