On 02/19/2014 04:56 PM, Russell Beall wrote:
Hi all,

We've just set up monster-sized server nodes to run 389 as a replacement to Sun DS.  I've been running my tests and I am pleased to report that the memory issue seems to be in check with growth only up to double the initial memory usage after large quantities of ldapmodify calls.  We have plenty of room in these boxes to accommodate caching the entire database.

The key blocker on this is still the ACL processing times for which I have been unable to find a decent resolution.  We have 135 ACIs at the root of the suffix.  When I comment out most of them but leave one service account active, processing times are very nicely fast.  When I leave them all on, that same service account takes 2.5 seconds to respond when only one request is pending.  A new kink in the puzzle here which is probably going to be a deal breaker is that if I run the same request on multiple threads, each thread takes proportionately longer to respond depending on the number of threads.  If I have 12 threads going doing a simple lookup, each thread responds in 45-55 seconds.  If I have 24 threads going, each thread takes 1m45s - 1m55s to respond.  The box has 32 cores available.  While processing, each thread is burning 100% of an available CPU thread for the entire time.  Theoretically when up to 32 requests are simultaneously processing, each thread should return in 2.5 seconds just as if it were one thread.

Note that the directory server performance does not scale linearly with the number of cores.  At some point you will run into thread contention.  Also things like replication compete for thread resources.

Since all threads are burning 100% the entire time, it doesn't seem like that would be caused by simple thread locking where some threads are waiting for others.

No, see below.

I'm thinking the system is not properly configured in some way and there is a system bottleneck blocking the processing.  When burning the CPU there is very little percentage allocated to the user percentage, most of the CPU usage is listed under the system CPU usage.  Is this normal, or is this indicative of some system layer that is bottlenecking the processing?

Sounds like the ACI may be doing some sort of unindexed internal search.

Have you narrowed it down to a particular ACI that is causing the problem?

Another question I posed earlier is whether or not it is possible to replicate three subtrees independently and then keep the aci entry at the root suffix independent so it can be set separately for multiple downstream replicants.  That way we could possibly subdivide the service accounts across different nodes.  Is that possible?



Russell Beall
Systems Programmer IV
Enterprise Identity Management
University of Southern California

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