RE: back-bdb deadlocks

["Howard Chu" <hyc@highlandsun.com>]

> -----Original Message-----
> From: Kurt D. Zeilenga [mailto:Kurt@OpenLDAP.org]

> Even that's pretty slow.  I see on my old FreeBSD devbox (2*P350)
> with userland threads (one execution context).  For -008:
>
>   1.323u 1.586s 1:18.83 3.6%      222+3232k 68+265io 148pf+0w
>
> Have you updated glibc/pthreads, did you completely rebuild bdb?
> I wonder if NGpthreads for Linux (from IBM) would help.

I've updated to glibc 2.2.4/linuxthreads 0.9, did not rebuild bdb after that.

Your db_stat results are interesting, 0 deadlocks. I can now get this
sometimes, but other times there are a few. I would expect this to be totally
non-deterministic. Must have something to do with thread scheduling
algorithms... With usermode threads you also need aio support, otherwise
any blocking I/O blocks all threads, making you effectively single-threaded.
That would certainly give deadlock-free execution.

> 1/2743070       File/offset for last checkpoint LSN.
> 0/0     No pending checkpoint LSN.
> Thu Jan 17 21:01:23 2002        Checkpoint timestamp.
> 80000136        Last transaction ID allocated.
> 20      Maximum number of active transactions possible.
> 0       Active transactions.
> 3       Maximum active transactions.
> 310     Number of transactions begun.
> 5       Number of transactions aborted.
> 305     Number of transactions committed.
> 0       Number of transactions restored.
> 16KB    Transaction region size (16384 bytes).
> 0       The number of region locks granted after waiting.
> 637     The number of region locks granted without waiting.
>
> 73 Last allocated locker ID.
> 9       Number of lock modes.
> 1000    Maximum number of locks possible.
> 1000    Maximum number of lockers possible.
> 1000    Maximum number of objects possible.
> 150846  Current locks.
> 150864  Maximum number of locks so far.
> 0       Current number of lockers.
> 22      Maximum number  lockers so far.
> 0       Current number lock objects.
> 16      Maximum number of lock objects so far.
> 178824  Number of lock requests.
> 178824  Number of lock releases.
> 0       Number of lock requests that would have waited.
> 699     Number of lock conflicts.
> 0       Number of deadlocks.
> 0       Number of transaction timeouts.
> 0       Number of lock timeouts.
> 352KB   Lock region size (360448 bytes).
> 19      The number of region locks granted after waiting.
> 199355  The number of region locks granted without waiting.
>

  -- Howard Chu
  Chief Architect, Symas Corp.       Director, Highland Sun
  http://www.symas.com               http://highlandsun.com/hyc
  Symas: Premier OpenSource Development and Support