Re: Reducing the chunk header sizes on all memory context types
От | Tom Lane |
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Тема | Re: Reducing the chunk header sizes on all memory context types |
Дата | |
Msg-id | 3209705.1661787794@sss.pgh.pa.us обсуждение исходный текст |
Ответ на | Re: Reducing the chunk header sizes on all memory context types (Tomas Vondra <tomas.vondra@enterprisedb.com>) |
Ответы |
Re: Reducing the chunk header sizes on all memory context types
Re: Reducing the chunk header sizes on all memory context types Re: Reducing the chunk header sizes on all memory context types |
Список | pgsql-hackers |
Tomas Vondra <tomas.vondra@enterprisedb.com> writes: > I suspect it's a pre-existing bug in Slab allocator, because it does this: > #define SlabBlockGetChunk(slab, block, idx) \ > ((MemoryChunk *) ((char *) (block) + sizeof(SlabBlock) \ > + (idx * slab->fullChunkSize))) > and SlabBlock is only 20B, i.e. not a multiple of 8B. Which would mean > that even if we allocate block and size the chunks carefully (with all > the MAXALIGN things), we ultimately slice the block incorrectly. Right, same conclusion I just came to. But it's not a "pre-existing" bug, because sizeof(SlabBlock) *was* maxaligned until David added another field to it. I think adding a padding field to SlabBlock would be a less messy solution than your patch. regards, tom lane
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