Christopher Browne <[EMAIL PROTECTED]> writes:"Stephen" <[EMAIL PROTECTED]> writes:Any chance we'll see the VACUUM delay patch (throttle) get into 7.5?
The hope, in 7.5, is to have ARC, which is the "super-duper-duper" version, working.
Actually, I'm not sure that ARC should be considered to supersede the usefulness of a per-page delay in VACUUM. ARC should prevent VACUUM from trashing the contents of Postgres' shared buffer arena, but it won't do much of anything to prevent VACUUM from trashing the kernel buffer contents. And it definitely won't do anything to help if the real problem is that you're short of disk bandwidth and VACUUM's extra I/O demand pushes your total load over the knee of the response-time curve. What you need then is a throttle.
The original patch I posted was incomplete for a number of reasons, but I think it may still be worth working on. Jan, any comments?
I agree that there is considerable value in IO distribution. As such I already have the basics of the Background Writer in there.
I left out the vacuum delay since I thought it was good enough to proove that there is low hanging fruit, but that it was far from what I'd call a solution. Ideally Vacuum would coordinate it's IO not only against some GUC variables, but also against the BGWriter+BufStrategy combo.
Jan
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