Of course you don't have a CPU bottleneck with curl, it does not run 3 or 4 hashes over everything it downloads. APT needs to hash its downloads to ensure they are secure, and it uses all available hashes to do so, so if one hash's security is compromised, we can still hopefully still rely on the others.
And the topic of this bug report is indeed hash CPU usage, and I compared our CPU usage on a 1 GB test file in a tmpfs to the CPU usage of OpenSSL and Nettle. So this test operates on a data size 5 times higher than the usual packages and under optimal conditions to evaluate how fast we can hash. The test shows that on a 1 Gbit/s connection you'll likely be throttled slightly at a comparable CPU (assuming the connection reaches about 800 Mbit/s, that is, 80% efficiency). If you have a data rate of about 500 Mbit/s, you will likely be fine (not counting parallel downloads). If there are other problems reducing the download speeds, these are separate bugs. This one covers the overhead of hashing, nothing else. BTW: The original bug report talks about 20% CPU usage on a 5 year old CPU, that seems entirely reasonable and not really an issue. If your bandwidth is high, you'll have higher CPU usage for a shorter time (like 100% for 5 seconds or so). -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1123272 Title: high cpu usage on download (not optimised SHA256, SHA512, SHA1) To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/apt/+bug/1123272/+subscriptions -- ubuntu-bugs mailing list [email protected] https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
