| From: | "Ideriha, Takeshi" <ideriha(dot)takeshi(at)jp(dot)fujitsu(dot)com> |
|---|---|
| To: | 'Robert Haas' <robertmhaas(at)gmail(dot)com>, Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com> |
| Cc: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Kyotaro HORIGUCHI <horiguchi(dot)kyotaro(at)lab(dot)ntt(dot)co(dot)jp>, Andres Freund <andres(at)anarazel(dot)de>, "Tsunakawa, Takayuki" <tsunakawa(dot)takay(at)jp(dot)fujitsu(dot)com>, Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>, Bruce Momjian <bruce(at)momjian(dot)us>, "PostgreSQL Hackers" <pgsql-hackers(at)lists(dot)postgresql(dot)org>, Michael Paquier <michael(dot)paquier(at)gmail(dot)com>, David Steele <david(at)pgmasters(dot)net>, Craig Ringer <craig(at)2ndquadrant(dot)com> |
| Subject: | RE: Protect syscache from bloating with negative cache entries |
| Date: | 2019-03-08 04:40:18 |
| Message-ID: | 4E72940DA2BF16479384A86D54D0988A6F448206@G01JPEXMBKW04 |
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| Lists: | pgsql-hackers |
>From: Robert Haas [mailto:robertmhaas(at)gmail(dot)com]
>On Thu, Mar 7, 2019 at 9:49 AM Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com>
>wrote:
>> I don't think this shows any regression, but perhaps we should do a
>> microbenchmark isolating the syscache entirely?
>
>Well, if we need the LRU list, then yeah I think a microbenchmark would be a good idea
>to make sure we really understand what the impact of that is going to be. But if we
>don't need it and can just remove it then we don't.
Just to be sure, we introduced the LRU list in this thread to find the entries less than threshold time
without scanning the whole hash table. If hash table becomes large without LRU list, scanning time becomes slow.
Regards,
Takeshi Ideriha
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