This bug was fixed in the package glibc - 2.27-3ubuntu1.3
---
glibc (2.27-3ubuntu1.3) bionic; urgency=medium
[ Balint Reczey ]
* debian/gbp.conf: Add initial configuration
* debian/control.in/main: Add Vcs-* pointing to Ubuntu packaging repository
* arm64: Enable searching
** Tags added: fr-211
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https://bugs.launchpad.net/bugs/1797335
Title:
strstr() on ubuntu18.04 8 times slower than on ubuntu16
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Verified 2.27-3ubuntu1.3 on Bionic:
root@bb-glibc:~# gcc strstr.c
root@bb-glibc:~# time ./a.out aa
matches = 300
real0m4.149s
user0m4.146s
sys 0m0.000s
root@bb-glibc:~# sed -i s/backports/proposed/ /etc/apt/sources.list
root@bb-glibc:~# apt update
Hit:1
Hello Paul, or anyone else affected,
Accepted glibc into bionic-proposed. The package will build now and be
available at https://launchpad.net/ubuntu/+source/glibc/2.27-3ubuntu1.3
in a few hours, and then in the -proposed repository.
Please help us by testing this new package. See
** Description changed:
- strstr() from glibc is up to 8 times slower than it was on ubuntu16.
- Looks like the sse2 optimized code is not used. To reproduce compile
- attached file (strstr.c) :
+ [Impact]
+ * Strstr() from glibc is up to 8 times slower than it was on ubuntu16.
+
+ [Test Case]
Fixed in glibc 2.29 and later, included in Ubuntu 19.04 and later.
** Changed in: glibc (Ubuntu)
Status: Confirmed => Fix Released
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Title:
** Changed in: glibc (Ubuntu Cosmic)
Status: New => Won't Fix
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Title:
strstr() on ubuntu18.04 8 times slower than on ubuntu16
To manage
** Also affects: glibc (Ubuntu Cosmic)
Importance: Undecided
Status: New
** Also affects: glibc (Ubuntu Bionic)
Importance: Undecided
Status: New
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** Tags added: id-5c094c3baba7ce7cee465e9c
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https://bugs.launchpad.net/bugs/1797335
Title:
strstr() on ubuntu18.04 8 times slower than on ubuntu16
To manage notifications about this
** Changed in: glibc (Ubuntu)
Status: Incomplete => Confirmed
** Changed in: glibc (Ubuntu)
Assignee: (unassigned) => Adam Conrad (adconrad)
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** Also affects: glibc via
https://sourceware.org/bugzilla/show_bug.cgi?id=23709
Importance: Unknown
Status: Unknown
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Title:
The bug has been opened on glibc and being (or already) fixed :
https://sourceware.org/bugzilla/show_bug.cgi?id=23709
Thanks
-Paul
** Bug watch added: Sourceware.org Bugzilla #23709
https://sourceware.org/bugzilla/show_bug.cgi?id=23709
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On my system, I can clearly see it selecting the sse2 implementation
(there is no AVX implementation of strstr)
$ gdb ./strstr
(gdb) break strstr
Breakpoint 1 at 0x1040
(gdb) run aa
Starting program: /home/adconrad/Downloads/strstr aa
Breakpoint 1, __strstr_sse2_unaligned () at
I notice that your cpu flags list avx2; this suggests the possibility
that the code path being used is one that's specific to avx2, not just
sse2. I have attempted to reproduce this on CPUs both with and without
avx2 and I cannot. I get no statistically-significant difference in
runtime, on
I can't reproduce this here. I'll note that I'm testing on a Broadwell
and you're on a Haswell, but I'd hope that doesn't make a huge
difference, unless H.J. Lu's latest round of CPU detection stuff has
gone amok.
model name : Intel(R) Core(TM) i7-5600U CPU @ 2.60GHz
$ file strstr
strstr: ELF 64-bit LSB shared object, x86-64, version 1 (SYSV), dynamically
linked, interpreter /lib64/ld-linux-x86-64.so.2, for GNU/Linux 3.2.0,
BuildID[sha1]=f09b9ae65046d6650a9b7007a9aa5d6d472a2d06, not stripped
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Yes, but to be absolutely certain, the `strstr` binary you created is a
64-bit binary?
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Title:
strstr() on ubuntu18.04 8 times slower than on
I'm running on amd64, i7 cpu :
$ lscpu
Architecture: x86_64
CPU op-mode(s): 32-bit, 64-bit
Byte Order: Little Endian
CPU(s): 8
On-line CPU(s) list: 0-7
Thread(s) per core: 2
Core(s) per socket: 4
Socket(s): 1
NUMA node(s): 1
Vendor ID: GenuineIntel
CPU family: 6
Model: 60
Model name: Intel(R)
Regarding:
$ gcc -o strstr strstr.c
Do you compile for i386 or amd64?
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Title:
strstr() on ubuntu18.04 8 times slower than on ubuntu16
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