| From: | Ants Aasma <ants(at)cybertec(dot)at> |
|---|---|
| To: | Merlin Moncure <mmoncure(at)gmail(dot)com> |
| Cc: | Robert Haas <robertmhaas(at)gmail(dot)com>, Florian Pflug <fgp(at)phlo(dot)org>, Sergey Koposov <koposov(at)ast(dot)cam(dot)ac(dot)uk>, Jeff Janes <jeff(dot)janes(at)gmail(dot)com>, pgsql-hackers(at)postgresql(dot)org, Stephen Frost <sfrost(at)snowman(dot)net> |
| Subject: | Re: 9.2beta1, parallel queries, ReleasePredicateLocks, CheckForSerializableConflictIn in the oprofile |
| Date: | 2012-06-04 15:42:41 |
| Message-ID: | CA+CSw_sS+T-wma9hQHBE7EGFx=OaX0jbuy81QZ1xDvRGFCeJyQ@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Mon, Jun 4, 2012 at 6:38 PM, Merlin Moncure <mmoncure(at)gmail(dot)com> wrote:
> On Mon, Jun 4, 2012 at 10:17 AM, Merlin Moncure <mmoncure(at)gmail(dot)com> wrote:
>> What happens (in the very unlikely, but possible case?) if another
>> backend races to the buffer you've pointed at with 'victim'? It looks
>> like multiple backends share the clock sweep now, but don't you need
>> to need an extra test to ensure it's still a candidate victim buffer?
>
> Actually, I don't think you do: the existing check on refcount is
> probably good enough. Hm, why did you get rid of
> BufferStrategyControl.lastFreeBuffer?
It was dead code as far as I could tell. That change isn't actually
relevant for this patch because free-list management is still
protected by a lock (except the initial unlocked test that is
doublechecked under lock) and so doesn't need any adjustment.
Ants Aasma
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