Re: Speed up Clog Access by increasing CLOG buffers

On Fri, Sep 11, 2015 at 11:01 PM, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
> If I am not wrong we need 1048576 number of transactions difference
> for each record to make each CLOG access a disk access, so if we
> increment XID counter by 100, then probably every 10000th (or multiplier
> of 10000) transaction would go for disk access.
>
> The number 1048576 is derived by below calc:
> #define CLOG_XACTS_PER_BYTE 4
> #define CLOG_XACTS_PER_PAGE (BLCKSZ * CLOG_XACTS_PER_BYTE)
>
> Transaction difference required for each transaction to go for disk access:
> CLOG_XACTS_PER_PAGE * num_clog_buffers.
>
> I think reducing to every 100th access for transaction status as disk access
> is sufficient to prove that there is no regression with the patch for the
> screnario
> asked by Andres or do you think it is not?

I have no idea. I was just suggesting that hacking the server somehow
might be an easier way of creating the scenario Andres was interested
in than the process you described. But feel free to ignore me, I
haven't taken much time to think about this.

--
Robert Haas
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