Re: SLRU optimization - configurable buffer pool and partitioning the SLRU lock

On Thu, Jan 25, 2024 at 10:03 PM Alvaro Herrera <alvherre@alvh.no-ip.org> wrote:
>
> On 2024-Jan-25, Alvaro Herrera wrote:
>
> > Here's a touched-up version of this patch.
>
> > diff --git a/src/backend/storage/lmgr/lwlock.c b/src/backend/storage/lmgr/lwlock.c
> > index 98fa6035cc..4a5e05d5e4 100644
> > --- a/src/backend/storage/lmgr/lwlock.c
> > +++ b/src/backend/storage/lmgr/lwlock.c
> > @@ -163,6 +163,13 @@ static const char *const BuiltinTrancheNames[] = {
> >       [LWTRANCHE_LAUNCHER_HASH] = "LogicalRepLauncherHash",
> >       [LWTRANCHE_DSM_REGISTRY_DSA] = "DSMRegistryDSA",
> >       [LWTRANCHE_DSM_REGISTRY_HASH] = "DSMRegistryHash",
> > +     [LWTRANCHE_COMMITTS_SLRU] = "CommitTSSLRU",
> > +     [LWTRANCHE_MULTIXACTOFFSET_SLRU] = "MultixactOffsetSLRU",
> > +     [LWTRANCHE_MULTIXACTMEMBER_SLRU] = "MultixactMemberSLRU",
> > +     [LWTRANCHE_NOTIFY_SLRU] = "NotifySLRU",
> > +     [LWTRANCHE_SERIAL_SLRU] = "SerialSLRU"
> > +     [LWTRANCHE_SUBTRANS_SLRU] = "SubtransSLRU",
> > +     [LWTRANCHE_XACT_SLRU] = "XactSLRU",
> >  };
>
> Eeek.  Last minute changes ...  Fixed here.

Thank you for working on this.  There is one thing that I feel is
problematic.  We have kept the allowed values for these GUCs to be in
multiple of SLRU_BANK_SIZE i.e. 16 and that's the reason the min
values were changed to 16 but in this refactoring patch for some of
the buffers you have changed that to 8 so I think that's not good.

+ {
+ {"multixact_offsets_buffers", PGC_POSTMASTER, RESOURCES_MEM,
+ gettext_noop("Sets the size of the dedicated buffer pool used for
the MultiXact offset cache."),
+ NULL,
+ GUC_UNIT_BLOCKS
+ },
+ &multixact_offsets_buffers,
+ 16, 8, SLRU_MAX_ALLOWED_BUFFERS,
+ check_multixact_offsets_buffers, NULL, NULL
+ },

Other than this patch looks good to me.

--
Regards,
Dilip Kumar
EnterpriseDB: http://www.enterprisedb.com