From: "Alex Xu (Hello71)" <alex_y_xu@yahoo.ca>
To: Michael Forney <forney@google.com>,
Masahiro Yamada <yamada.masahiro@socionext.com>,
Michal Marek <michal.lkml@markovi.net>,
Nick Desaulniers <ndesaulniers@google.com>,
Nick Terrell <terrelln@fb.com>, Ingo Molnar <mingo@kernel.org>,
Sedat Dilek <sedat.dilek@gmail.com>,
Kees Cook <keescook@chromium.org>,
linux-kernel@vger.kernel.org, linux-kbuild@vger.kernel.org
Cc: "Alex Xu (Hello71)" <alex_y_xu@yahoo.ca>
Subject: [PATCH v2 2/2] kbuild: pass --stream-size --no-content-size to zstd
Date: Wed, 24 Nov 2021 10:31:05 -0500 [thread overview]
Message-ID: <20211124153105.155739-2-alex_y_xu@yahoo.ca> (raw)
In-Reply-To: <20211124153105.155739-1-alex_y_xu@yahoo.ca>
Otherwise, it allocates 2 GB of memory at once. Even though the majority
of this memory is never touched, the default heuristic overcommit
refuses this request if less than 2 GB of RAM+swap is currently
available. This results in "zstd: error 11 : Allocation error : not
enough memory" and the kernel failing to build.
When the size is specified, zstd will reduce the memory request
appropriately. For typical kernel sizes of ~32 MB, the largest mmap
request will be reduced to 512 MB, which will succeed on all but the
smallest devices.
For inputs around this size, --stream-size --no-content-size may
slightly decrease the compressed size, or slightly increase it:
https://github.com/facebook/zstd/issues/2848.
Signed-off-by: Alex Xu (Hello71) <alex_y_xu@yahoo.ca>
---
scripts/Makefile.lib | 12 ++++++++++--
1 file changed, 10 insertions(+), 2 deletions(-)
diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib
index ca901814986a..c98a82ca38e6 100644
--- a/scripts/Makefile.lib
+++ b/scripts/Makefile.lib
@@ -466,12 +466,20 @@ quiet_cmd_xzmisc = XZMISC $@
# single pass, so zstd doesn't need to allocate a window buffer. When streaming
# decompression is used, like initramfs decompression, zstd22 should likely not
# be used because it would require zstd to allocate a 128 MB buffer.
+#
+# --stream-size to reduce zstd memory usage (otherwise zstd -22 --ultra
+# allocates, but does not use, 2 GB) and potentially improve compression.
+#
+# --no-content-size to save three bytes which we do not use (we use size_append).
+
+# zstd --stream-size is only supported since 1.4.4
+zstd_stream_size = $(shell $(ZSTD) -1c --stream-size=0 --no-content-size </dev/null >/dev/null 2>&1 && printf '%s' '--stream-size=$(total_size) --no-content-size')
quiet_cmd_zstd = ZSTD $@
- cmd_zstd = { cat $(real-prereqs) | $(ZSTD) -19; $(size_append); } > $@
+ cmd_zstd = { cat $(real-prereqs) | $(ZSTD) $(zstd_stream_size) -19; $(size_append); } > $@
quiet_cmd_zstd22 = ZSTD22 $@
- cmd_zstd22 = { cat $(real-prereqs) | $(ZSTD) -22 --ultra; $(size_append); } > $@
+ cmd_zstd22 = { cat $(real-prereqs) | $(ZSTD) $(zstd_stream_size) -22 --ultra; $(size_append); } > $@
# ASM offsets
# ---------------------------------------------------------------------------
--
2.34.0
next prev parent reply other threads:[~2021-11-24 15:30 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20211124153105.155739-1-alex_y_xu.ref@yahoo.ca>
2021-11-24 15:31 ` [PATCH v2 1/2] kbuild: use perl instead of shell to get file size Alex Xu (Hello71)
2021-11-24 15:31 ` Alex Xu (Hello71) [this message]
2021-12-03 0:49 ` [PATCH v2 2/2] kbuild: pass --stream-size --no-content-size to zstd Nick Terrell
2021-12-05 22:52 ` Masahiro Yamada
2021-12-06 18:42 ` Nick Terrell
2021-12-17 8:51 ` Sedat Dilek
2021-12-17 13:44 ` Sedat Dilek
2021-12-03 0:45 ` [PATCH v2 1/2] kbuild: use perl instead of shell to get file size Nick Terrell
2021-12-17 13:45 ` Sedat Dilek
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