[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] Linux v3.12 + pv ticketlocks
On Wed, Sep 11, 2013 at 09:05:05PM +0200, Sander Eikelenboom wrote: > > Wednesday, September 11, 2013, 8:41:29 PM, you wrote: > > > On Wed, Sep 11, 2013 at 08:25:01PM +0200, Sander Eikelenboom wrote: > >> Hi Konrad, > >> > >> Just to confirm: > >> > >> - PV ticketlocks is on by default and doesn't neet a config option, to > >> disable it at boot time it's possible to use "xen_nopvspin" as a kernel > >> commandline parameter > > > Yes. > >> - CONFIG_PARAVIRT_SPINLOCKS should be off, since that would enable the old > >> bytelock pv-spinlock implementation which could now probably be removed ? > > > You still need CONFIG_PARAVIRT_SPINLOCKS=y to take advantage of it. > > > The bytelock pvspinlock is gone. If you compile without > > CONFIG_PARAVIRT_SPINLOCKS > > then you will only use ticketlocks for all types of guests and baremtal. No > > 'PV' variant. > > > The CONFIG_PARAVIRT_SPINLOCKS=y enables the PV ticketlock for all guests. > > Ok so the KConfig (help) entry for CONFIG_PARAVIRT_SPINLOCKS should perhaps > also be updated ? Yes! > > Since it for example still contains the "Unfortunately the downside is an up > to 5% > performance hit on native kernels, with various workloads." which afaik was > one the things the PV ticketlock migitated, > so it would be more feasible for distributions to have this option on for all > general distro kernels ? Yikes. That is true - needs to be updated as the results were the opposite: Results: ======= setup: 32 core machine with 32 vcpu KVM guest (HT off) with 8GB RAM base = 3.11-rc patched = base + pvspinlock V12 +-----------------+----------------+--------+ dbench (Throughput in MB/sec. Higher is better) +-----------------+----------------+--------+ | base (stdev %)|patched(stdev%) | %gain | +-----------------+----------------+--------+ | 15035.3 (0.3) |15150.0 (0.6) | 0.8 | | 1470.0 (2.2) | 1713.7 (1.9) | 16.6 | | 848.6 (4.3) | 967.8 (4.3) | 14.0 | | 652.9 (3.5) | 685.3 (3.7) | 5.0 | +-----------------+----------------+--------+ (I don't have the baremetal one - but it was pretty much 0%). Please if you get a chance - please do send a patch to x86 folks altering this. Thanks! _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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