Date: Tue, 23 Nov 2010 10:35:02 +0000 From: David Xu <davidxu@freebsd.org> To: Ivan Voras <ivoras@freebsd.org> Cc: freebsd-performance@freebsd.org Subject: Re: PostgreSQL performance scaling Message-ID: <4CEB98D6.40902@freebsd.org> In-Reply-To: <AANLkTikyK_q1Uw%2BSWHB9EMTNRgiQhA9frhdUYy7KoQF_@mail.gmail.com> References: <iccd37$lhh$1@dough.gmane.org> <op.vmj44dm634t2sn@skeletor.lan> <4CEA9C46.8010507@freebsd.org> <icf1nk$192$1@dough.gmane.org> <icf36a$8ik$1@dough.gmane.org> <4CEB8AEF.7030202@freebsd.org> <AANLkTikyK_q1Uw%2BSWHB9EMTNRgiQhA9frhdUYy7KoQF_@mail.gmail.com>
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Ivan Voras wrote: > On 23 November 2010 10:35, David Xu <davidxu@freebsd.org> wrote: >> Ivan Voras wrote: > >>> and the overall behaviour is similar - the processes spend a lot of time >>> in "sbwait" and "ksem" states. >>> >> Strange, the POSIX semaphore in head branch does not use ksem, it is >> based on umtx, there is no limit on POSIX semaphore, the only limit >> is process's address space which limits how many semaphores can be >> used. > > *shrug*; I don't know how it could be wrong - this PostgreSQL was > built from ports after I upgraded & booted 9-current. > > If it didn't use POSIX semaphores from HEAD, shared semaphores > wouldn't have worked, right? > It may work, but even it is shared in memory, it still enters kernel to do P/V operation.
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