| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Greg Stark <stark(at)mit(dot)edu> |
| Cc: | Robert Haas <robertmhaas(at)gmail(dot)com>, Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com>, Peter Geoghegan <pg(at)heroku(dot)com>, Pg Hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: rethinking dense_alloc (HashJoin) as a memory context |
| Date: | 2016-07-18 14:32:02 |
| Message-ID: | 22452.1468852322@sss.pgh.pa.us |
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| Lists: | pgsql-hackers |
Greg Stark <stark(at)mit(dot)edu> writes:
> I wonder if we could go further. If we don't imagine having a very
> large number of allocators then we could just ask each one in turn if
> this block is one of theirs and which context it came from. That would
> allow an allocator that just allocated everything in a contiguous
> block to recognize pointers and return the memory context just by the
> range the pointer lies in.
The performance problem is not "large number of allocators", it's "large
number of distinct memory ranges". Also, this will fail utterly to
recognize duplicate-pfree and bad-pointer cases. Not that the existing
method is bulletproof, but this way has zero robustness against caller
bugs.
regards, tom lane
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