Re: Protect syscache from bloating with negative cache entries

From: Kyotaro HORIGUCHI <horiguchi(dot)kyotaro(at)lab(dot)ntt(dot)co(dot)jp>
To: michael(dot)paquier(at)gmail(dot)com
Cc: Jim(dot)Nasby(at)bluetreble(dot)com, tgl(at)sss(dot)pgh(dot)pa(dot)us, robertmhaas(at)gmail(dot)com, craig(at)2ndquadrant(dot)com, pgsql-hackers(at)postgresql(dot)org
Subject: Re: Protect syscache from bloating with negative cache entries
Date: 2017-02-01 06:25:43
Message-ID: 20170201.152543.14165695.horiguchi.kyotaro@lab.ntt.co.jp
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Hello, thank you for moving this to the next CF.

At Wed, 1 Feb 2017 13:09:51 +0900, Michael Paquier <michael(dot)paquier(at)gmail(dot)com> wrote in <CAB7nPqRFhUv+GX=eH1bo7xYHS79-gRj1ecu2QoQtHvX9RS=JYA(at)mail(dot)gmail(dot)com>
> On Tue, Jan 24, 2017 at 4:58 PM, Kyotaro HORIGUCHI
> <horiguchi(dot)kyotaro(at)lab(dot)ntt(dot)co(dot)jp> wrote:
> > Six new syscaches in 665d1fa was conflicted and 3-way merge
> > worked correctly. The new syscaches don't seem to be targets of
> > this patch.
>
> To be honest, I am not completely sure what to think about this patch.
> Moved to next CF as there is a new version, and no new reviews to make
> the discussion perhaps move on.

I'm thinking the following is the status of this topic.

- The patch stll is not getting conflicted.

- This is not a hollistic measure for memory leak but surely
saves some existing cases.

- Shared catcache is another discussion (and won't really
proposed in a short time due to the issue on locking.)

- As I mentioned, a patch that caps the number of negative
entries is avaiable (in first-created - first-delete manner)
but it is having a loose end of how to determine the
limitation.

regards,

--
Kyotaro Horiguchi
NTT Open Source Software Center

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