On 06.03.2012 14:52, Fujii Masao wrote:
On Tue, Mar 6, 2012 at 2:17 AM, Tom Lane<t...@sss.pgh.pa.us>  wrote:
Heikki Linnakangas<heikki.linnakan...@enterprisedb.com>  writes:
On 21.02.2012 13:19, Fujii Masao wrote:
In some places, the spinlock "insertpos_lck" is taken while another
spinlock "info_lck" is being held. Is this OK? What if unfortunately
inner spinlock takes long to be taken?

Hmm, that's only done at a checkpoint (and a restartpoint), so I doubt
that's a big issue in practice. We had the same pattern before the
patch, just with WALInsertLock instead of insertpos_lck. Holding a
spinlock longer is much worse than holding a lwlock longer, but
nevertheless I don't think that's a problem.

No, that's NOT okay.  A spinlock is only supposed to be held across a
short straight-line sequence of instructions.

Ok, that's easy enough to fix.

This also strikes me that the usage of the spinlock insertpos_lck might
not be OK in ReserveXLogInsertLocation() because a few dozen instructions
can be performed while holding the spinlock....

I admit that block is longer than any of our existing spinlock blocks. However, it's important for performance. I tried using a lwlock earlier, and that negated the gains. So if that's a serious objection, then let's resolve that now before I spend any more time on other aspects of the patch. Any ideas how to make that block shorter?

  Heikki Linnakangas
  EnterpriseDB   http://www.enterprisedb.com

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