Date: Tue, 11 Feb 2014 10:36:24 -0800 From: Colin Percival <cperciva@freebsd.org> To: "Justin T. Gibbs" <gibbs@scsiguy.com>, Karl Pielorz <kpielorz_lst@tdx.co.uk> Cc: freebsd-xen@FreeBSD.org Subject: Re: FreeBSD 10.0-R as Xen 'guest' - clarification? Message-ID: <52FA6DA8.7030107@freebsd.org> In-Reply-To: <7EC86263-B19E-4829-A601-F78DEDCEF7E9@scsiguy.com> References: <18819F918745D984B618D518@Mail-PC.tdx.co.uk> <7EC86263-B19E-4829-A601-F78DEDCEF7E9@scsiguy.com>
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On 02/11/14 09:26, Justin T. Gibbs wrote:=0D > On Jan 29, 2014, at 8:28 AM, Karl Pielorz <kpielorz_lst@tdx.co.uk> wrote:= =0D >> The man page for xen (man 4 xen) states you should have:=0D >>=0D >> options NO_ADAPTIVE_MUTEXES=0D >> options NO_ADAPTIVE_RWLOCKS=0D >> options NO_ADAPTIVE_SX=0D > =0D > The =93NO_ADAPTIVE=94 settings are an optimization when running in enviro= nments where different guests run on the same physical CPU. However, many = cloud providers seem to statically pin CPUs to VMs, which means the adaptiv= e lock optimization works as expected.=0D =0D ... and with static pinning, adding the NO_ADAPTIVE_FOO options causes a=0D significant drop in performance, so you really don't want them unless you'r= e=0D going to be sharing CPUs.=0D =0D -- =0D Colin Percival=0D Security Officer Emeritus, FreeBSD | The power to serve=0D Founder, Tarsnap | www.tarsnap.com | Online backups for the truly paranoid
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