Re: Bgwriter strategies

On 7/11/07, Heikki Linnakangas <heikki(at)enterprisedb(dot)com> wrote:
>
> I was able
> to reproduce the phenomenon with a simple C program that writes 8k
> blocks in random order to a fixed size file. I've attached it along with
> output of running it on my test server. The output shows how the writes
> start to periodically block after a while. I was able to reproduce the
> problem on my laptop as well. Can anyone explain what's going on?
>
>
>
I think you are assuming that the next write of the same block won't
use another OS cache block. I doubt if thats the way writes are handled
by the kernel. Each write would typically end up being queued up in the
kernel
where each write will have its own copy of the block to the written. Isn't
it ?

Thanks,
Pavan

--
Pavan Deolasee
EnterpriseDB http://www.enterprisedb.com