Date: Tue, 18 Jun 2013 11:21:51 -1000 (HST) From: Jeff Roberson <jroberson@jroberson.net> To: Alfred Perlstein <bright@mu.org> Cc: src-committers@freebsd.org, Andre Oppermann <andre@freebsd.org>, svn-src-all@freebsd.org, Gleb Smirnoff <glebius@FreeBSD.org>, svn-src-head@freebsd.org, Jeff Roberson <jeff@FreeBSD.org> Subject: Re: svn commit: r251894 - in head: lib/libmemstat sys/vm Message-ID: <alpine.BSF.2.00.1306181118310.2005@desktop> In-Reply-To: <51C04C77.7010907@mu.org> References: <201306180450.r5I4oKoY091256@svn.freebsd.org> <51C01964.1000006@freebsd.org> <20130618083733.GQ1400@FreeBSD.org> <51C04C77.7010907@mu.org>
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On Tue, 18 Jun 2013, Alfred Perlstein wrote: > On 6/18/13 4:37 AM, Gleb Smirnoff wrote: >> On Tue, Jun 18, 2013 at 10:25:08AM +0200, Andre Oppermann wrote: >> A> There used to be a problem with per CPU caches accumulating large >> amounts >> A> of items without freeing back to the global (or socket) pool. >> A> >> A> Do these updates to UMA change this situation and/or do you have further >> A> improvements coming up? >> >> This is especially a problem with ZFS, which utilizes UMA extensively. >> >> IMHO, we need a flag for uma_zcreate() that would disable per CPU caches, >> so >> that certain zones (ZFS at least) would have them off. >> >> It might be a good idea to force this flag on every zone that has >> allocation >= >> then the page size. >> > What about people running with 256GB+ ram? Do they also want the per cpu > caches off? If you look at the new system there is a static threshold for the initial item size required for different sized per-cpu buckets. What might make sense is to tune this size based on available memory. For what it's worth I looked at solaris settings and they cache roughly 4x as much on a per-cpu basis. The new system should tend to cache less of large and infrequent allocations vs the old system. I can't say yet whether it is still a problem. I have an implementation of vmem to replace using vm_maps for kmem_map, buffer_map, etc. which may resolve the zfs allocation problems. I hope to get this in over the next few weeks. Thanks, Jeff > > -- > Alfred Perlstein > VP Software Engineering, iXsystems >
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