Re: wip-librbd-caching

[Sage Weil <sage@xxxxxxxxxxxx>]

On Wed, 18 Apr 2012, Martin Mailand wrote:
> Am 12.04.2012 21:45, schrieb Sage Weil:
> > The config options you'll want to look at are client_oc_* (in case you
> > didn't see that already :).  "oc" is short for objectcacher, and it isn't
> > only used for client (libcephfs), so it might be worth renaming these
> > options before people start using them.
> 
> Hi,
> 
> I changed the values and the performance is still very good and the memory
> footprint is much smaller.
> 
> OPTION(client_oc_size, OPT_INT, 1024*1024* 50)    // MB * n
> OPTION(client_oc_max_dirty, OPT_INT, 1024*1024* 25)    // MB * n  (dirty OR
> tx.. bigish)
> OPTION(client_oc_target_dirty, OPT_INT, 1024*1024* 8) // target dirty (keep
> this smallish)
> // note: the max amount of "in flight" dirty data is roughly (max - target)
> 
> But I am not quite sure about the meaning of the values.
> client_oc_size Max size of the cache?

yes

> client_oc_max_dirty max dirty value before the writeback starts?

before writes block and wait for writeback to bring the dirty level down

> client_oc_target_dirty ???

before writeback starts

BTW I renamed 'rbd cache enabled' -> 'rbd cache'.  I'd like to rename the 
objectcacher settings too so they aren't nested under client_ (which is 
the fs client code).

objectcacher_*?

sage
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