Re: Using per-transaction memory contexts for storing decoded tuples

On Wed, Oct 16, 2024 at 10:32 AM Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com> wrote:
>
> On Tue, Oct 15, 2024 at 9:01 PM Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
> >
> > On Tue, Oct 15, 2024 at 11:15 PM Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com> wrote:
> > >
> > > On Sun, Oct 13, 2024 at 11:00 PM Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
> > > >
> > > > On Fri, Oct 11, 2024 at 3:40 AM Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com> wrote:
> > > > >
> > > > > Please find the attached patches.
> > > > >
> > >
> > > Thank you for reviewing the patch!
> > >
> > > >
> > > > @@ -343,9 +343,9 @@ ReorderBufferAllocate(void)
> > > > */
> > > > buffer->tup_context = GenerationContextCreate(new_ctx,
> > > > "Tuples",
> > > > - SLAB_LARGE_BLOCK_SIZE,
> > > > - SLAB_LARGE_BLOCK_SIZE,
> > > > - SLAB_LARGE_BLOCK_SIZE);
> > > > + SLAB_DEFAULT_BLOCK_SIZE,
> > > > + SLAB_DEFAULT_BLOCK_SIZE,
> > > > + SLAB_DEFAULT_BLOCK_SIZE);
> > > >
> > > > Shouldn't we change the comment atop this change [1] which states that
> > > > we should benchmark the existing values?
> > >
> > > Agreed.
> > >
> >
> > Can we slightly tweak the comments as follows so that it doesn't sound
> > like a fix for a bug?
> >
> > /* To minimize memory fragmentation caused by long-running
> > transactions with changes spanning multiple memory blocks, we use a
> > single fixed-size memory block for decoded tuple storage. The tests
> > showed that the default memory block size maintains logical decoding
> > performance without causing fragmentation due to concurrent
> > transactions. One might think that we can use the max size as
> > SLAB_LARGE_BLOCK_SIZE but the test also showed it doesn't help resolve
> > the memory fragmentation.
>
> Agreed. I've incorporated your comment in the latest patches. I'm
> going to push them today, barring any objections or further comments.

Pushed. Thank you all for reviewing and testing the patch.

Regards,

--
Masahiko Sawada
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