Date: Wed, 11 Aug 2004 15:29:50 +0000 From: Bosko Milekic <bmilekic@FreeBSD.org> To: Andre Oppermann <andre@freebsd.org>, freebsd-current@freebsd.org Subject: Re: UMA questions Message-ID: <20040811152950.GA17794@freefall.freebsd.org>
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>1. UMA zones do not show up in the output of 'vmstat -m'. Is there a way > to get information on how much memory each UMA zone is using? > Example: "sackhole", "tcptw", ... vmstat -z, or sysctl vm.zone. Be careful when interpreting the stats in the Mbuf, Mbuf Cluster, and Packet zones, because they are special. See www.unixdaemons.com/~bmilekic/netbuf_bmilekic.pdf if you want to know why, exactly. >2. What does the flag UMA_ZONE_ZINIT do exactly? It initializes zone-allocated objects to zero. This happens as objects are first allocated (i.e., slabs are allocated) and before placement into the slab cache. Unfortunately, I am not sure this works very well unless you also make sure to zero them as they are returned (dtor), which is a shitty model. >3. What does the flag UMA_ZONE_NOFREE prevent exactly? Will it prevent any > zone/slab of this type to be free'd ever again? This way the zone can > only grow and not shrink after transient peaks? Yes. It prevents freeing/draining of the slab cache. -Bosko
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