From: | "Mikheev, Vadim" <vmikheev(at)SECTORBASE(dot)COM> |
---|---|
To: | "'Tom Lane'" <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | pgsql-hackers(at)postgreSQL(dot)org |
Subject: | RE: Re: Strangeness in xid allocation / snapshot setup |
Date: | 2001-07-12 18:48:27 |
Message-ID: | 3705826352029646A3E91C53F7189E320166C9@sectorbase2.sectorbase.com |
Views: | Raw Message | Whole Thread | Download mbox | Resend email |
Thread: | |
Lists: | pgsql-hackers |
> >> Given this, I'm wondering why we bother with having a separate
> >> XidGenLock spinlock at all. Why not eliminate it and use SInval
> >> spinlock to lock GetNewTransactionId and ReadNewTransactionId?
>
> > Reading all MyProc in GetSnashot may take long time - why disallow
> > new Tx to begin.
>
> Because we need to synchronize? It bothers me that we're assuming
> that fetching/storing XIDs is atomic. There's no possibility at all
> of going to 8-byte XIDs as long as the code is like this.
>
> I doubt that a spinlock per PROC structure would be a better answer,
> either; the overhead of getting and releasing each lock would be
> nontrivial, considering the small number of instructions spent at
> each PROC in these routines.
Isn't spinlock just a few ASM instructions?... on most platforms...
Vadim
From | Date | Subject | |
---|---|---|---|
Next Message | Tom Lane | 2001-07-12 18:50:38 | Re: Rule recompilation |
Previous Message | P. Dwayne Miller | 2001-07-12 18:45:09 | select count... |