Re: [HACKERS] Re: Faster CREATE DATABASE by delaying fsync (was 8.4.1 ubuntu karmic slow createdb)

On 02/03/10 14:42, Robert Haas wrote:
> On Wed, Feb 3, 2010 at 6:53 AM, Greg Stark<gsstark(at)mit(dot)edu> wrote:
>> On Tue, Feb 2, 2010 at 7:45 PM, Robert Haas<robertmhaas(at)gmail(dot)com> wrote:
>>> I think you're probably right, but it's not clear what the new name
>>> should be until we have a comment explaining what the function is
>>> responsible for.
>>
>> So I wrote some comments but wasn't going to repost the patch with the
>> unchanged name without explanation... But I think you're right though
>> I was looking at it the other way around. I want to have an API for a
>> two-stage sync and of course if I do that I'll comment it to explain
>> that clearly.
>>
>> The gist of the comments was that the function is preparing to fsync
>> to initiate the i/o early and allow the later fsync to fast -- but
>> also at the same time have the beneficial side-effect of avoiding
>> cache poisoning. It's not clear that the two are necessarily linked
>> though. Perhaps we need two separate apis, though it'll be hard to
>> keep them separate on all platforms.
>
> Well, maybe we should start with a discussion of what kernel calls
> you're aware of on different platforms and then we could try to put an
> API around it.
In linux there is sync_file_range. On newer Posixish systems one can
emulate that with mmap() and msync() (in batches obviously).

No idea about windows.

Andres