On Fri, 2018-09-07 at 13:38 -0600, David Boreham wrote: > > On 9/6/2018 6:37 PM, William Brown wrote: > > > > I have seen this behaviour due to an issue in the design of access > > log > > buffer flushing. During a buffer flush all other threads are > > delayed, > > which can cause this spike. > > > > You can confirm this by changing your access log buffer size up or > > down. > > > > Sadly this problem is not simply fixed without a complete rewrite > > of > > the logging subsystem - which I would love to do, but I am not > > employed > > to work on 389 at this time so I lack the time. > > > > > > Interesting to see this because when I first ran performance tests > on > the DS, around 20 years ago, I quickly discovered that the logging > code > was a bottleneck. So I re-wrote it with in-memory ping-pong > buffering > for the operation threads' log output, and removed any synchronous > filesystem writes. I expect that in the years since perhaps > concurrency > bugs led to that that code being removed, or it could be that it no > longer performs well with modern hardware. Could be both. Modern hardware is especially bad at handling any situation where locking get's involved due to the highly async nature of modern CPU's and their cache layers. There is a lot on my "todo list" to rearchitect to make the code scalable on modern systems today. A lot of what I want to do is directly inspired by erlang's actor model and concurrent readability. > > _______________________________________________ > 389-users mailing list -- 389-users@xxxxxxxxxxxxxxxxxxxxxxx > To unsubscribe send an email to > 389-users-leave@xxxxxxxxxxxxxxxxxxxxxxx > Fedora Code of Conduct: https://getfedora.org/code-of-conduct.html > List Guidelines: > https://fedoraproject.org/wiki/Mailing_list_guidelines > List Archives: > https://lists.fedoraproject.org/archives/list/389-users@xxxxxxxxxxxxxxxxxxxxxxx -- Sincerely, William _______________________________________________ 389-users mailing list -- 389-users@xxxxxxxxxxxxxxxxxxxxxxx To unsubscribe send an email to 389-users-leave@xxxxxxxxxxxxxxxxxxxxxxx Fedora Code of Conduct: https://getfedora.org/code-of-conduct.html List Guidelines: https://fedoraproject.org/wiki/Mailing_list_guidelines List Archives: https://lists.fedoraproject.org/archives/list/389-users@xxxxxxxxxxxxxxxxxxxxxxx
