Re: [PATCH] Refactoring of LWLock tranches

On Thu, Feb 11, 2016 at 6:45 PM, Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
>
> On Thu, Feb 11, 2016 at 3:15 AM, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>
wrote:
> > Sounds sensible, however after changes, CreateLWLocks() started
> > looking unreadable, so moved initialization and registration of tranches
> > to separate functions.
>
> Seems good.
>
> > Increased number of tranches allocated in LWLockTrancheArray, as
> > now the LWTRANCHE_FIRST_USER_DEFINED is already greater
> > than 16.
>
> OK, cool.
>
> + int numIndividualLocks =
NUM_INDIVIDUAL_LWLOCKS;
> + int numBufMappingLocks =
NUM_BUFFER_PARTITIONS;
> + int numLmgrLocks = NUM_LOCK_PARTITIONS;
> + int i;
>
> This doesn't seem like it's buying us anything. Can't we just use the
> constants directly?
>

Yes, we can use the constants. The reason I have used variables
was they need to be used at couple of places, but I think using
constants directly also doesn't harm, so changed accordingly.

> + BufMappingLWLockTranche.name = "Buffer Mapping Locks";
>
> We've not been very consistent about how we name our tranches. If
> we're going to try to expose this information to users, we're going to
> need to do better. We've got these names:
>
> main
> clog
> commit_timestamp
> subtrans
> multixact_offset
> multixact_member
> async
> oldserxid
> WALInsertLocks
> Buffer Content Locks
> Buffer IO Locks
> ReplicationOrigins
> Replication Slot IO Locks
> proc
>
> Personally, I prefer the style of all lower case, words separated with
> semicolons where necessary, the word "locks" left out. That way we
> can display wait events as something like lwlock:<name of tranche> and
> not have the word "lock" in there twice. I don't think it does much
> good to try to make these names "user friendly" because,
> fundamentally, these are internal pieces of the system and you won't
> know what they are unless you do. So I'd prefer to make them look
> like identifiers. If we adopt that style, then I think the new
> tranches created by this patch should be named buffer_mapping,
> lock_manager, and predicate_lock_manager

Okay, changed as per suggestion.

> and then, probably as a
> separate patch, we should rename the rest to match that style
> (buffer_content, buffer_io, replication_origin, replication_slot_io).
>

Sure, will send these changes as a separate patch.

With Regards,
Amit Kapila.
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