| From: | Dan Ports <drkp(at)csail(dot)mit(dot)edu> |
|---|---|
| To: | Robert Haas <robertmhaas(at)gmail(dot)com> |
| Cc: | Kevin Grittner <Kevin(dot)Grittner(at)wicourts(dot)gov>, Simon Riggs <simon(at)2ndQuadrant(dot)com>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: SSI non-serializable UPDATE performance |
| Date: | 2011-04-29 07:23:56 |
| Message-ID: | 20110429072356.GF1432@csail.mit.edu |
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| Lists: | pgsql-hackers |
On Thu, Apr 28, 2011 at 06:45:54PM +0200, Robert Haas wrote:
> Yeah, I think Dan's notes about memory ordering would be good to include.
I left it out initially because I didn't want to make things more
confusing. As far as memory ordering is concerned, this is the same
story as anything else that uses lwlocks: the spinlock memory barrier
prevents memory accesses from being reordered before the lock is
acquired. The only unusual thing here is that the lock in question
isn't the one that protects the variable we're reading.
But I'm OK with adding a comment if you think it helps. Patch attached.
Dan
--
Dan R. K. Ports MIT CSAIL http://drkp.net/
| Attachment | Content-Type | Size |
|---|---|---|
| ssi-memory-ordering-comment.patch | text/x-diff | 723 bytes |
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