| From: | Robert Haas <robertmhaas(at)gmail(dot)com> |
|---|---|
| To: | Jeff Davis <pgsql(at)j-davis(dot)com> |
| Cc: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, pgsql-hackers(at)postgresql(dot)org |
| Subject: | Re: Removing PD_ALL_VISIBLE |
| Date: | 2012-11-26 21:03:37 |
| Message-ID: | CA+TgmobTZHXfMPMAU6NNGWUNEeM8ZtVCAS2r5QWjU60L6t3KGw@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Mon, Nov 26, 2012 at 3:29 PM, Jeff Davis <pgsql(at)j-davis(dot)com> wrote:
> Your intuition here is better than mine, but I am still missing
> something here. If we keep the buffer pinned, then there will be very
> few pin/unpin cycles here, so I don't see where the contention would
> come from (any more than there is contention pinning the root of an
> index).
Based on previous measurements, I think there *is* contention pinning
the root of an index. Currently, I believe it's largely overwhelmed
by contention from other sources, such as the buffer manager lwlocks
and the very-evil ProcArrayLock. However, I believe that as we fix
those problems, this will start to percolate up towards the top of the
heap.
--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company
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