Re: [Lsf-pc] Linux kernel impact on PostgreSQL performance

On Wed, Jan 15, 2014 at 4:35 AM, Jan Kara <jack@suse.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