Re: [HACKERS] Moving relation extension locks out of heavyweight lock manager - Mailing list pgsql-hackers

From Dilip Kumar
Subject Re: [HACKERS] Moving relation extension locks out of heavyweight lock manager
Date
Msg-id CAFiTN-t-NttZBabhKkbVHX7iSdXzmXZHXCVNKddk5Pxfi2WScw@mail.gmail.com
Whole thread Raw
In response to Re: [HACKERS] Moving relation extension locks out of heavyweight lock manager  (Kuntal Ghosh <kuntalghosh.2007@gmail.com>)
List pgsql-hackers
On Fri, Mar 13, 2020 at 2:32 PM Kuntal Ghosh <kuntalghosh.2007@gmail.com> wrote:
>
> On Fri, Mar 13, 2020 at 8:29 AM Amit Kapila <amit.kapila16@gmail.com> wrote:
> >
> > On Thu, Mar 12, 2020 at 7:50 PM Kuntal Ghosh <kuntalghosh.2007@gmail.com> wrote:
> > > I think moving them inside a macro is a good idea. Also, I think we
> > > should move all the Assert related code inside some debugging macro
> > > similar to this:
> > > #ifdef LOCK_DEBUG
> > > ....
> > > #endif
> > >
> > If we move it under some macro, then those Asserts will be only
> > enabled when that macro is defined.  I think we want there Asserts to
> > be enabled always in assert enabled build, these will be like any
> > other Asserts in the code.  What is the advantage of doing those under
> > macro?
> >
> My concern is related to performance regression. We're using two
> static variables in hot-paths only for checking a few asserts. So, I'm
> not sure whether we should enable the same by default, specially when
> asserts are itself disabled.
> -ResetRelExtLockHeldCount()
> +ResetRelExtPageLockHeldCount()
>  {
>   RelationExtensionLockHeldCount = 0;
> + PageLockHeldCount = 0;
> +}
> Also, we're calling this method from frequently used functions like
> Commit/AbortTransaction. So, it's better these two static variables
> share the same cache line and reinitalize them with a single
> instruction.

In the recent version of the patch, instead of a counter, we have done
with a flag.  So I think now we can just keep a single variable and we
can just reset the bit in a single instruction.

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



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