** 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] + * Compile and run the attached strstr.c test on an affected Haswell CPU. For the exact Haswell model see the upstream bug report, Qemu can be used to emulate the right model. + * Observe much faster execution times with the fixed glibc package. + + [Regression Potential] + + * The fix changes the per-model CPU feautures handling in a very + specific way fixing a previous change in the same area. Regressions here + are unlikely, but could in theory cause slowdowns, crashes and + miscalculations if the wrong CPU features are becoming used. + + [Original Bug Text] + 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) : $ gcc -o strstr strstr.c and then run on the 2 platforms : $ vagrant init ubuntu/bionic64 $ vagrant up $ vagrant ssh Welcome to Ubuntu 18.04.1 LTS (GNU/Linux 4.15.0-36-generic x86_64) * Documentation: https://help.ubuntu.com * Management: https://landscape.canonical.com * Support: https://ubuntu.com/advantage System information as of Thu Oct 11 09:02:46 UTC 2018 System load: 0.0 Processes: 97 Usage of /: 9.8% of 9.63GB Users logged in: 0 Memory usage: 12% IP address for enp0s3: 10.0.2.15 Swap usage: 0% * Security certifications for Ubuntu! We now have FIPS, STIG, CC and a CIS Benchmark. - http://bit.ly/Security_Certification * Want to make a highly secure kiosk, smart display or touchscreen? Here's a step-by-step tutorial for a rainy weekend, or a startup. - https://bit.ly/secure-kiosk Get cloud support with Ubuntu Advantage Cloud Guest: http://www.ubuntu.com/business/services/cloud 0 packages can be updated. 0 updates are security updates. Last login: Thu Oct 11 09:02:17 2018 from 10.0.2.2 vagrant@ubuntu-bionic:~$ cd /vagrant vagrant@ubuntu-bionic:/vagrant$ time ./strstr aa matches = 3000000 real 0m4.877s user 0m4.852s sys 0m0.012s vagrant@ubuntu-bionic:/vagrant$ Same machine : $ vagrant init ubuntu/xenial64 $ vagrant up $ vagrant ssh Welcome to Ubuntu 16.04.5 LTS (GNU/Linux 4.4.0-135-generic x86_64) * Documentation: https://help.ubuntu.com * Management: https://landscape.canonical.com * Support: https://ubuntu.com/advantage Get cloud support with Ubuntu Advantage Cloud Guest: http://www.ubuntu.com/business/services/cloud 0 packages can be updated. 0 updates are security updates. New release '18.04.1 LTS' available. Run 'do-release-upgrade' to upgrade to it. Last login: Thu Oct 11 08:22:26 2018 from 10.0.2.2 vagrant@ubuntu-xenial:~$ cd /vagrant vagrant@ubuntu-xenial:/vagrant$ time ./strstr aa matches = 3000000 real 0m0.525s user 0m0.508s sys 0m0.000s vagrant@ubuntu-xenial:/vagrant$ vagrant@ubuntu-xenial:/vagrant$ time ./strstr aa matches = 3000000 real 0m0.525s user 0m0.508s sys 0m0.000s vagrant@ubuntu-xenial:/vagrant$
-- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1797335 Title: strstr() on ubuntu18.04 8 times slower than on ubuntu16 To manage notifications about this bug go to: https://bugs.launchpad.net/glibc/+bug/1797335/+subscriptions -- ubuntu-bugs mailing list [email protected] https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
