Re: Add bump memory context type and use it for tuplesorts

[Andres Freund]

Hi,

On 2024-04-07 22:35:47 +0200, Tomas Vondra wrote:
> I haven't investigated, but I'd considering it works on 64-bit, I guess
> it's not considering alignment somewhere. I can dig more if needed.

I think I may the problem:


#define KeeperBlock(set) ((BumpBlock *) ((char *) (set) + sizeof(BumpContext)))
#define IsKeeperBlock(set, blk) (KeeperBlock(set) == (blk))

BumpContextCreate():
...
        /* Fill in the initial block's block header */
        block = (BumpBlock *) (((char *) set) + MAXALIGN(sizeof(BumpContext)));
        /* determine the block size and initialize it */
        firstBlockSize = allocSize - MAXALIGN(sizeof(BumpContext));
        BumpBlockInit(set, block, firstBlockSize);
...
        ((MemoryContext) set)->mem_allocated = allocSize;

void
BumpCheck(MemoryContext context)
...
                if (IsKeeperBlock(bump, block))
                        total_allocated += block->endptr - (char *) bump;
...

I suspect that KeeperBlock() isn't returning true, because IsKeeperBlock misses
the MAXALIGN(). I think that about fits with:

> #4  0x008f0088 in BumpCheck (context=0x131e330) at bump.c:808
> 808             Assert(total_allocated == context->mem_allocated);
> (gdb) p total_allocated
> $1 = 8120
> (gdb) p context->mem_allocated
> $2 = 8192


Greetings,

Andres Freund