Re: [HACKERS] strange behaviour on pooled alloc

> Hi,
>
> I'm continuing with the pooled palloc() stuff and am stuck
> with a very strange thing. I've reverted my changes to
> palloc() and am doing all the memory block pool handling now
> in aset.c.
>
> The benefit from this will be that I later can easily make
> palloc() etc. macros.

Sounds good.

> The new version of the AllocSet...() functions does not use
> ordered set. it manages the block pools itself. Has the same
> 10% speedup and I expect some more from the macro version of
> palloc(). It aligns small allocations to power of 2 for
> better reusability of free'd chunks which are held in 8
> different free lists per alloc set depending on their size.
> It lost the ability of AllocSetDump() - who need's that?

No one.

>
> First I found some bad places where memory is used after it
> has been free'd. One was in the portal manager with a portal
> memory context struct! I'm pretty sure that I found all
> because I tested by memset() 'ing all memory on
> AllocSetFree() and AllocSetReset() with different values.

Good.

> The strange behaviour now is that depending on the blocksize
> and the limit for block/single alloction I use for the pools,
> the portals_p2 regression test fails or not. The failure is
> that the cursor foo24 does not return data if the pools
> blocksize is greater/equal 16K and the smallchunk limit is
> 2K. It returns the correct row if one of them is less. More
> irritating is that it only fails if run inside 'make
> runtest'. If I put multiple portals_p2 tests into the tests
> list, all fail the same. But if the test is run manually with
> the same psql switches, it succeeds.
>
> All this behaviour is identical on two Linux 2.1.88
> installations. One has gcc-2.8.1 and glibc-2.0.13, the other
> gcc-2.7.2.1 and libc.5.
>
> I have absolutely no clue what's going on here. Anyone an
> idea how to track this down?

My recommendation is to apply the fix and let others debug it. Someone
will find the cause. Just give them a reproducable test case. In many
cases, more eyes or another OS shows the error much clearer.

--
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