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: > On Jan 29, 2014, at 8:28 AM, Karl Pielorz <kpielorz_lst@tdx.co.uk> wrote: >> The man page for xen (man 4 xen) states you should have: >> >> options NO_ADAPTIVE_MUTEXES >> options NO_ADAPTIVE_RWLOCKS >> options NO_ADAPTIVE_SX > > The “NO_ADAPTIVE” settings are an optimization when running in environments where different guests run on the same physical CPU. However, many cloud providers seem to statically pin CPUs to VMs, which means the adaptive lock optimization works as expected. ... and with static pinning, adding the NO_ADAPTIVE_FOO options causes a significant drop in performance, so you really don't want them unless you're going to be sharing CPUs. -- Colin Percival Security Officer Emeritus, FreeBSD | The power to serve Founder, Tarsnap | www.tarsnap.com | Online backups for the truly paranoidhelp
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