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Jeroen W. Pluimers on .NET, C#, Delphi, databases, and personal interests

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Archive for March 20th, 2019

Some notes on loosing performance because of using AVX

Posted by jpluimers on 2019/03/20

It looks like AVX can be a curse most of the times. Below are some (many) links that lead me to this conclusion, based on a thread started by Kelly Sommers.

My conclusion

Running AVX instructions will affect the processor frequency, which means that non-AVX code will slow down, so you will only benefit when the gain of using AVX code outweighs the non-AVX loss on anything running on that processor in the same time frame.

In practice, this means you need to long term gain from AVX on many cores. If you don’t, then the performance penalty on all cores, including the initial AVX performance, will degrade, often a lot (dozens of %).

Tweets and pages linked by them

Kelly raised a bunch of interesting questions and remarks because of the above:

I collected the above links because of [WayBack] GitHub – maximmasiutin/FastMM4-AVX: FastMM4 fork with AVX support and multi-threaded enhancements (faster locking), where it is unclear which parts of the gains are because of AVX and which parts are because of other optimizations. It looks like that under heavy loads on data center like conditions, the total gain is about 30%. The loss for traditional processing there has not been measured, but from the above my estimate it is at least 20%.

Full tweets below.

Read the rest of this entry »

Posted in Assembly Language, Development, Software Development, x64, x86 | Leave a Comment »

Keep a Changelog

Posted by jpluimers on 2019/03/20

Lot’s of tips (and translations!) on how to Keep a Changelog [WayBack].

There are lots of useful tips, ranging from content (how to write, what to include) to technicalities (order of entries, unreleased, version numbering, date format) that might seem unimportant but in practice makes using the changelog.

The really cool thing: the site has a changelog of itself showing the best practices.

via:

–jeroen

Posted in Development, Documentation Development, Encryption, Let's Encrypt (letsencrypt/certbot), Security, Software Development | Leave a Comment »

During git mv (rename): “unable to unlink old” “invalid argument”

Posted by jpluimers on 2019/03/20

I had an error when doing a rename (mv) in git “unable to unlink old” “invalid argument”. This appeared to be a process having a lock on that file.

In my case, this was a bit hard to track down (I used Process Explorer for it), as the culprit was SourceTree running git in the background to keep an eye on changes in the repository because it has a file system watcher on the repository tree and a different process was writing log files in the same directory structure.

Can you still follow? I had a hard time so here it is in manageable bits:

  1. By default SourceTree has a file system watcher on your repositories
  2. If that watcher fires, SourceTree runs a background git process to get the current state of the repository
  3. If you perform UI actions, SourceTree runs a foreground git process to perform the action
  4. SourceTree does not have a mechanism to wait for the background git process to finish before running the foreground process
  5. I had had another process running that logged into a relative directory that happened to be within the repository tree (but using files excluded by .gitignore)

Basically SourceTree should do two things:

  • keep track of the background process and not fire a foreground one
  • do not start the background process for files excluded by .gitignore

I tracked down what happened using these tips:

–jeroen

Posted in Development, DVCS - Distributed Version Control, git, Source Code Management | Leave a Comment »

 
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