On Mon, 15 Jan 2007, Dennis Clarke wrote: > > > Justin Gombos wrote: > > > >> There is a ZFS FAQ somewhere indicating that ZFS *appears* to hog > >> memory because it uses as much as it can, but it supposedly > >> relinquishes memory as soon as an app calls for it. > >> > >> I thought that should be pointed out, though I am not quick to accept > >> it myself. How does the kernel ask ZFS processes for more memory? > > > > ZFS uses kmem_cache_create() and friends, which is a fun little beast. > > It can manufacture and recycle pre-initialized bits of memory without > > having to do much to it. One of the arguments used in setting up a > > cache is a callback routine the kernel memory allocator can call when > > it needs subsystems to clean up and return memory to the system. > > > > In the particular case of the ZFS ARC cache, there's a hdr_cache and > > a buf_cache; the hdr_cache has a callback, which wakes up the ARC > > reclaim thread to evict unneeded allocations in several areas, not > > just that one cache. > > This has probably been asked before but is there a kernel tunable that > will restrict the high water mark for ZFS cache memory? This way I could > just grant 50% of mamory and no more. That sort of thing.
Hi Dennis, Yes - see: <URL:http://bugs.opensolaris.org/bugdatabase/view_bug.do?bug_id=6505658> > A more important question would be, what effect would this have on system > performance and am I merely thwarting progress. Sort of like early owners > of the automobile were forced to send someone walking in front of them > with a light in order to ensure that the horses were not frightened. That > sort of thing. The best (IMHO) answer is to try it on your system with your workload. Bear in mind that the ZFS developers are adamant that there should be no tunables and that the system should handle every situation automatically. Regards, Al Hopper Logical Approach Inc, Plano, TX. [EMAIL PROTECTED] Voice: 972.379.2133 Fax: 972.379.2134 Timezone: US CDT OpenSolaris.Org Community Advisory Board (CAB) Member - Apr 2005 OpenSolaris Governing Board (OGB) Member - Feb 2006 _______________________________________________ opensolaris-discuss mailing list [email protected]
