| From: | Robert Haas <robertmhaas(at)gmail(dot)com> |
|---|---|
| To: | Jan Kara <jack(at)suse(dot)cz> |
| Cc: | Heikki Linnakangas <hlinnakangas(at)vmware(dot)com>, Jim Nasby <jim(at)nasby(dot)net>, Andres Freund <andres(at)2ndquadrant(dot)com>, Josh Berkus <josh(at)agliodbs(dot)com>, Hannu Krosing <hannu(at)2ndquadrant(dot)com>, "lsf-pc(at)lists(dot)linux-foundation(dot)org" <lsf-pc(at)lists(dot)linux-foundation(dot)org>, Kevin Grittner <kgrittn(at)ymail(dot)com>, "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org>, Dave Chinner <david(at)fromorbit(dot)com>, Joshua Drake <jd(at)commandprompt(dot)com>, Bottomley James <James(dot)Bottomley(at)hansenpartnership(dot)com>, Claudio Freire <klaussfreire(at)gmail(dot)com>, Mel Gorman <mgorman(at)suse(dot)de>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Trond Myklebust <trondmy(at)gmail(dot)com>, Magnus Hagander <magnus(at)hagander(dot)net> |
| Subject: | Re: [Lsf-pc] Linux kernel impact on PostgreSQL performance |
| Date: | 2014-01-15 15:12:38 |
| Message-ID: | CA+TgmoY2J6-fCaaruh9hEDAveOQBJkF9Oq9oG0uMbw1p9vzL9w@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Wed, Jan 15, 2014 at 4:35 AM, Jan Kara <jack(at)suse(dot)cz> wrote:
> Filesystems could in theory provide facility like atomic write (at least up
> to a certain size say in MB range) but it's not so easy and when there are
> no strong usecases fs people are reluctant to make their code more complex
> unnecessarily. OTOH without widespread atomic write support I understand
> application developers have similar stance. So it's kind of chicken and egg
> problem. BTW, e.g. ext3/4 has quite a bit of the infrastructure in place
> due to its data=journal mode so if someone on the PostgreSQL side wanted to
> research on this, knitting some experimental ext4 patches should be doable.
Atomic 8kB writes would improve performance for us quite a lot. Full
page writes to WAL are very expensive. I don't remember what
percentage of write-ahead log traffic that accounts for, but it's not
small.
--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company
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