Tom Lane wrote:
> Bruce Momjian <pgman@candle.pha.pa.us> writes:
> > ITAGAKI Takahiro wrote:
> >> Bruce Momjian <pgman@candle.pha.pa.us> wrote:
> >>> I looked this over and I am unsure what this does for us that isn't
> >>> already accomplished using the wal_sync_method settings. See xlog.c for
> >>> a description of O_DIRECT and when it is used.
> >>
> >> I proposed it to supplement the cache control. There are some OSes that
> >> supports posix_fadvise but not O_DIRECT, for example, NetBSD 4.0
> >> (http://www.netbsd.org/Changes/changes-4.0.html).
>
> > Oh, that makes sense then. Let me re-add it to the queue.
>
> Could we see some performance measurements *from those OSes*? The given
> test on Linux certainly does not justify adding another operating
> system dependency to the WAL code. For that matter, even if it is a big
> win on some versions of NetBSD, I'm not sure I'd want to accept it ...
> how many NetBSD users do we have who would care?
>
> Depending on OS features we have never depended on before is a *huge*
> ongoing maintenance cost, and I have not seen an argument that I think
> justifies this one.
I disagree. It is a localized change and seems like a win, and it uses
a standard POSIX feature, rather than an OS-specific one.
I fact the patch cleans up our code by centralizing the WAL close() code
and error message.
--
Bruce Momjian | http://candle.pha.pa.us
pgman@candle.pha.pa.us | (610) 359-1001
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