From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
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To: | Andres Freund <andres(at)anarazel(dot)de> |
Cc: | Heikki Linnakangas <hlinnaka(at)iki(dot)fi>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: Excessive PostmasterIsAlive calls slow down WAL redo |
Date: | 2018-04-05 18:39:27 |
Message-ID: | 18771.1522953567@sss.pgh.pa.us |
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Lists: | pgsql-hackers |
Andres Freund <andres(at)anarazel(dot)de> writes:
> ISTM the better approach would be to try to reduce the cost of
> PostmasterIsAlive() on common platforms - it should be nearly free if
> done right.
+1 if it's doable.
> One way to achieve that would e.g. to stop ignoring SIGPIPE and instead
> check for postmaster death inside the handler, without reacting to
> it. Then the the actual PostmasterIsAlive() checks are just a check of a
> single sig_atomic_t.
AFAIR, we do not get SIGPIPE on the postmaster pipe, because nobody
ever writes to it. So this sketch seems off to me, even assuming that
not-ignoring SIGPIPE causes no problems elsewhere.
While it's not POSIX, at least some platforms are capable of delivering
a separate signal on parent process death. Perhaps using that where
available would be enough of an answer.
regards, tom lane
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