| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Simon Riggs <simon(at)2ndquadrant(dot)com> |
| Cc: | josh(at)agliodbs(dot)com, pgsql-hackers(at)postgresql(dot)org, testperf-general(at)pgfoundry(dot)org |
| Subject: | Re: [Testperf-general] Re: ExclusiveLock |
| Date: | 2004-11-18 23:54:41 |
| Message-ID: | 21504.1100822081@sss.pgh.pa.us |
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| Lists: | pgsql-hackers |
Simon Riggs <simon(at)2ndquadrant(dot)com> writes:
> Can we subdivide the WALInsertLock so there are multiple entry points to
> wal_buffers, based upon hashing the xid?
I don't think so; WAL is inherently a linear log. (Awhile ago there was
some talk of nonlinear log writing to get around the one-commit-per-
disk-revolution syndrome, but the idea basically got rejected as
unworkably complicated.) What's more, there are a lot of entries that
must remain time-ordered independently of transaction ownership.
Consider btree index page splits and sequence nextvals for two examples.
Certainly I'd not buy into any such project without incontrovertible
proof that it would solve a major bottleneck --- and right now we are
only speculating with no evidence.
regards, tom lane
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