> From: Dave Chinner [mailto:da...@fromorbit.com] > Sent: Thursday, January 03, 2013 12:34 AM > Subject: Re: [PATCH 7/8] zswap: add to mm/ > > > > On 01/02/2013 09:26 AM, Dan Magenheimer wrote: > > > > However if one compares the total percentage > > > > of RAM used for zpages by zswap vs the total percentage of RAM > > > > used by slab, I suspect that the zswap number will dominate, > > > > perhaps because zswap is storing primarily data and slab is > > > > storing primarily metadata? > > > > > > That's *obviously* 100% dependent on how you configure zswap. But, that > > > said, most of _my_ systems tend to sit with about 5% of memory in > > > reclaimable slab > > > > The 5% "sitting" number for slab is somewhat interesting, but > > IMHO irrelevant here. The really interesting value is what percent > > is used by slab when the system is under high memory pressure; I'd > > imagine that number would be much smaller. True? > > Not at all. The amount of slab memory used is wholly dependent on > workload. I have plenty of workloads with severe memory pressure > that I test with that sit at a steady state of >80% of ram in slab > caches. These workloads are filesytem metadata intensive rather than > data intensive, that's exactly the right cache balance for the > system to have....
Hey Dave -- I'd like to do some zcache policy testing where the severe memory pressure is a result of something like the above where >80% of ram is in slab caches. Any thoughts on how to do this or easily simulate it on a very simple hardware system (e.g. PC with one SATA disk)? Or is a "big data" configuration required? Thanks for any advice! Dan -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
