[OpenAFS-devel] Default params for afsd?

[Troy Benjegerdes]

On Fri, May 13, 2005 at 12:43:42PM -0400, Jeffrey Hutzelman wrote:
> On Friday, May 13, 2005 09:43:05 AM +0200 Niklas Edmundsson 
> <Niklas.Edmundsson@hpc2n.umu.se> wrote:
> 
> >I have a faint memory of the memcache only being able to store
> >cachesize/chunksize number of files even if the files are much smaller
> >than chunksize, ie that the memcache is an array of chunksize blocks. If
> >this is correct, then you should probably reduce the chunksize when doing
> >small-sized-memcache to be able to fit enough files.
> 
> You bring up an important point which I failed to mention.  The proposals I 
> made regarding chunkSize, cacheFiles, and dCacheSize are all relevant only 
> when using disk cache.  The memory cache architecture works somewhat 
> differently; memcache chunks are fixed-size and take up the same amount of 
> storage regardless of how "full" they are.  So, the cache can store only 
> cachesize/chunksize chunks.
> 
> As you suggested, this argues for much smaller chunks than would be used 
> for a disk cache, and in fact the default chunkSize for memcache is only 13 
> (8K).  I'm not suggesting changing this default, though of course folks who 
> think they can spare the memory could choose to raise it (and cacheBlocks) 
> an order of magnitude or two.

When I was messing around trying to get anything close to 10% of gigabit
wire speeds, I found the best performance with a 100mb memcache, and
chunkSize set to either 18 or 20.

Is there a way to set the network transfer size independent from the
chunk size, or are these somewhat inextricably linked?