improve 2x-3x sha256sum performance on ppc64le due to current gcc optimization bug
Affects | Status | Importance | Assigned to | Milestone | |
---|---|---|---|---|---|
coreutils (Debian) |
Fix Released
|
Unknown
|
|||
coreutils (Ubuntu) |
Fix Released
|
Undecided
|
Matthias Klose | ||
Xenial |
Fix Released
|
Undecided
|
Unassigned | ||
Yakkety |
Fix Released
|
Undecided
|
Unassigned |
Bug Description
[Impact]
* Performance drop of 2x-3x on ppc64le when using sha256sum
* Please backport this bug to last LTS as this application is widely used.
* This fix is due to a optimization issue found on gcc v4.9 to gcc v7.0.
[Test Case]
* Run sha256sum with a big file and measure the time it takes. The patch improves this timing up to 3 times faster.
[Regression Potential]
* This patch is specifically for the sha256.o object, affecting only this binary.
[Other Info]
Michael Stone's improved patch:
Index: coreutils-
=======
--- coreutils-
+++ coreutils-
@@ -14661,6 +14661,10 @@
$(TEST_LOGS): $(PROGRAMS)
+ifeq ($(DEB_
+lib/sha256.o: CFLAGS+
+endif
+
# Tell versions [3.59,3.63) of GNU make to not export all variables.
# Otherwise a system limit (for SysV at least) may be exceeded.
.NOEXPORT:
Original bug description:
The sha256sum provided by coreutils (without openssl) is performing
poorly with gcc versions >= 4.9 until 7.0 (currently under development).
The reason for that is the -fschedule-insns optimization that is used
with -O2. By simply deactivating it, there is a performance improvement
of 2 to 3 times.
I'm using Ubuntu 16.10 and the coreutils package version 8.25-2ubuntu2.
Please check the following closed debian bug report:
https:/
Be aware of the following conditions that are required:
* If ppc64le
* If gcc being used is >= 4.9 and < 7.0
Notes:
1) gcc-7 is not affected by this bug (verified on 20170129 snapshot).
2) clang is not affected by this bug (verified on v3.8 and v3.9).
3) strangely the sha512 is not affected by this.
Below a demonstration of how it performs on my POWER8 machine:
=======
$ (./configure && make -j9) > /dev/null && time src/sha256sum ~/ubuntu-
configure: WARNING: libacl development library was not found or not usable.
configure: WARNING: GNU coreutils will be built without ACL support.
configure: WARNING: libattr development library was not found or not usable.
configure: WARNING: GNU coreutils will be built without xattr support.
configure: WARNING: libcap library was not found or not usable.
configure: WARNING: GNU coreutils will be built without capability support.
configure: WARNING: libgmp development library was not found or not usable.
configure: WARNING: GNU coreutils will be built without GMP support.
src/who.c: In function 'print_user':
src/who.c:454:20: warning: initialization discards 'const' qualifier from pointer target type [-Wdiscarded-
int *a = utmp_ent-
d14bdb413ea6cdc
real 0m18.670s
user 0m16.566s
sys 0m0.745s
$ # now with the following patch: ## Check Michael Stone's patch for an improved version.
$ diff Makefile.in ../Makefile.in
8989c8989
< @am__fastdepCC_
---
> @am__fastdepCC_
$ cp ../Makefile.in Makefile.in
$ (./configure && make -j9) > /dev/null && time src/sha256sum ~/ubuntu-
configure: WARNING: libacl development library was not found or not usable.
configure: WARNING: GNU coreutils will be built without ACL support.
configure: WARNING: libattr development library was not found or not usable.
configure: WARNING: GNU coreutils will be built without xattr support.
configure: WARNING: libcap library was not found or not usable.
configure: WARNING: GNU coreutils will be built without capability support.
configure: WARNING: libgmp development library was not found or not usable.
configure: WARNING: GNU coreutils will be built without GMP support.
src/who.c: In function 'print_user':
src/who.c:454:20: warning: initialization discards 'const' qualifier from pointer target type [-Wdiscarded-
int *a = utmp_ent-
d14bdb413ea6cdc
real 0m5.903s
user 0m5.560s
sys 0m0.255s
tags: | added: yakkety |
Changed in coreutils (Ubuntu): | |
assignee: | nobody → Matthias Klose (doko) |
Changed in coreutils (Debian): | |
status: | Unknown → Fix Released |
description: | updated |
tags: | added: verification-done |
One other possibility (as performed by Fedora) is to have libcrypto (from openssl) configured through the "--with- openssl= yes" parameter.