Re: Spread checkpoint sync

Josh Berkus wrote:
> On 11/20/10 6:11 PM, Jeff Janes wrote:
>> True, but I think that changing these from their defaults is not
>> considered to be a dark art reserved for kernel hackers, i.e they are
>> something that sysadmins are expected to tweak to suite their work
>> load, just like the shmmax and such.
>
> I disagree. Linux kernel hackers know about these kinds of parameters,
> and I suppose that Linux performance experts do. But very few
> sysadmins, in my experience, have any idea.

To me, a lot of this conversation feels parallel to the
arguments the occasionally come up debating writing directly
to raw disks bypassing the filesystems altogether.

Might smoother checkpoints be better solved by talking
to the OS vendors & virtual-memory-tunning-knob-authors
to work with them on exposing the ideal knobs; rather than
saying that our only tool is a hammer(fsync) so the problem
must be handled as a nail.

Hypothetically - what would the ideal knobs be?

Something like madvise WONTNEED but that leaves pages
in the OS's cache after writing them?