[389-users] Re: ldap perfomance

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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