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.
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