Re: Clock sweep not caching enough B-Tree leaf pages?

On Thu, Apr 17, 2014 at 2:28 PM, Stephen Frost <sfrost@snowman.net> wrote:
>
>
> On Thursday, April 17, 2014, Merlin Moncure <mmoncure@gmail.com> wrote:
>>
>> yeah -- the thing is, we are already too spendy already on
>> supplemental write i/o (hint bits, visible bits, freezing, etc) and
>> likely not worth it to throw something else on the pile unless the
>> page is already dirty; the medium term trend in storage is that read
>> vs write performance is becoming increasingly asymmetric, particularly
>> on the random side so it's very unlikely to balance out.
>
> Guess I wasn't clear but I was thinking to read the page in, not do any
> writing, and do it in a asynchronous way to the process doing the evicting.

no -- I got you. My point was, that's a pure guess unless you base it
on evidence recorded on the page itself.  Without that evidence,
(which requires writing) the operating is in a a better place to make
that guess so it's probably better to defer that decision.

merlin