| From: | Simon Riggs <simon(at)2ndQuadrant(dot)com> |
|---|---|
| To: | Fujii Masao <masao(dot)fujii(at)gmail(dot)com> |
| Cc: | Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>, pgsql-hackers(at)postgresql(dot)org, Daniel Farina <daniel(at)heroku(dot)com> |
| Subject: | Re: Sync Rep v17 |
| Date: | 2011-03-01 08:21:14 |
| Message-ID: | 1298967674.12992.3210.camel@ebony |
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| Lists: | pgsql-hackers |
On Tue, 2011-03-01 at 15:51 +0900, Fujii Masao wrote:
> Thanks for update of the patch!
>
> On Tue, Mar 1, 2011 at 3:40 AM, Simon Riggs <simon(at)2ndquadrant(dot)com> wrote:
> >> SyncRepRemoveFromQueue seems not to be as short-term as we can
> >> use the spinlock. Instead, LW lock should be used there.
>
> You seem to have forgotten to fix the above-mentioned issue.
Not forgotten.
> A spinlock can be used only for very short-term operation like
> read/write of some shared-variables. The operation on the queue
> is not short, so should be protected by LWLock, I think.
There's no need to sleep while holding locks and the operations are very
short in most cases. The code around it isn't trivial, but that's no
reason to use LWlocks.
LWlocks are just spinlocks plus sem sleeps, so I don't see the need for
that in the current code. Other views welcome.
--
Simon Riggs http://www.2ndQuadrant.com/books/
PostgreSQL Development, 24x7 Support, Training and Services
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