[Glass] gc settings

Otto Behrens otto at finworks.biz
Fri Feb 14 13:35:14 PST 2014

Thanks a lot. Trying it out.

On Fri, Feb 14, 2014 at 9:44 PM, Dale Henrichs
<dale.henrichs at gemtalksystems.com> wrote:
> Otto,
> I talked this over with one of the guys here and he suggests that the trick
> is to not create shadow pages faster than the gc gem can handle them ... the
> gcgems are pretty aggreessive by default ...
> He suggests that you  commit frequently and the  monitor the
> PagesNeedsReclaiming stat in your migration loop and when it gets above a
> certain threshold (a couple thousand pages?) stop migrating and go into an
> "idle loop" where you abort (to avoid CR backlog and allow pages to run
> through their normal life cycle) and check for the stat to drop below
> another threshold (250 pages? once it's below your threshold get going again
> ...
> regarding the epoch gc. the become operation does not itself generate a lot
> of dead if you dow a become between a persistent object and a temp object
> and commit, the temp object will be written as the persist object and no
> garbage will be produced ... you will however create shadowpages as the new
> versions of the objects are copied to new pages (page reclaim is why the
> gcgems get revved up) ... now if you are creating short-lived persist
> objects as some other part of your  migration process then an epoch will
> help keep those dead boys in check ...
> Dale
> On Fri, Feb 14, 2014 at 4:07 AM, Otto Behrens <otto at finworks.biz> wrote:
>> Hi,
>> Do you have a set of GcUser settings that we can use for aggressive
>> garbage collection during a migration process? We would like to do the
>> garbage collection (epoch and reclaim) while the migration process is
>> generating a lot of dead stuff. We don't mind if the migration takes a
>> bit longer. We do mind if the migration generates a lot of free space
>> in the extent.
>> Thanks
>> Otto
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