| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Robert Haas <robertmhaas(at)gmail(dot)com> |
| Cc: | Fujii Masao <masao(dot)fujii(at)gmail(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: bug in SignalSomeChildren |
| Date: | 2010-12-17 16:12:17 |
| Message-ID: | 579.1292602337@sss.pgh.pa.us |
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| Lists: | pgsql-hackers |
Robert Haas <robertmhaas(at)gmail(dot)com> writes:
> On Fri, Dec 17, 2010 at 10:27 AM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>> I'm not really thrilled at the idea of calling
>> IsPostmasterChildWalSender for every child whether or not it will have
>> any impact on the decision. That involves touching shared memory which
>> can be rather expensive (see previous discussions about shared cache
>> lines and so forth).
> The existing code already does that, unless I'm missing something.
No, it only makes that call when it's actually relevant to the decision
and it's exhausted all other possible tests. In particular, the call is
never made for target = ALL which I think is the common case.
regards, tom lane
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