| From: | Ants Aasma <ants(dot)aasma(at)eesti(dot)ee> |
|---|---|
| To: | "Tsunakawa, Takayuki" <tsunakawa(dot)takay(at)jp(dot)fujitsu(dot)com> |
| Cc: | "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Is the unfair lwlock behavior intended? |
| Date: | 2016-05-24 20:39:27 |
| Message-ID: | CA+CSw_uCLbNCRPYU12OmCj_8Ghc9Mv-Qy5uyR36TaDLb94L1Zg@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Tue, May 24, 2016 at 9:03 AM, Tsunakawa, Takayuki
<tsunakawa(dot)takay(at)jp(dot)fujitsu(dot)com> wrote:
> I encountered a strange behavior of lightweight lock in PostgreSQL 9.2. That appears to apply to 9.6, too, as far as I examine the code. Could you tell me if the behavior is intended or needs fix?
>
> Simply put, the unfair behavior is that waiters for exclusive mode are overtaken by share-mode lockers who arrive later.
9.5 had significant LWLock scalability improvements. This might
improve performance enough so that exclusive lockers don't get
completely starved. It would be helpful if you could test if it's
still possible to trigger starvation with the new code.
Regards,
Ants Aasma
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