[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] VM memory allocation speed with cs 26056
On 12/11/2012 15:01, "Zhigang Wang" <zhigang.x.wang@xxxxxxxxxx> wrote: > Hi Keir/Jan, > > Recently I got a chance to access a big machine (2T mem/160 cpus) and I tested > your patch: http://xenbits.xen.org/hg/xen-unstable.hg/rev/177fdda0be56 > > Attached is the result. The PVM result is weird, there is a small-ish slowdown for small domains, becoming a very large %age slowdown as domain memory increases, and then turning into a *speedup* as the memory size gets very large indeed. What are the error bars like on these measurements I wonder? One thing we could do to allow PV guests doing 4k-at-a-time allocations through alloc_heap_pages() to benefit from the TLB-flush improvements, is pull the filtering-and-flush out into populate_physmap() and increase_reservation(). This is listed as a todo in the original patch (26056). To be honest I don't know why the original patch would make PV domain creation slower, and certainly not by a varying %age depending on domain memory size! -- Keir > Test environment old: > > # xm info > host : ovs-3f-9e-04 > release : 2.6.39-300.17.1.el5uek > version : #1 SMP Fri Oct 19 11:30:08 PDT 2012 > machine : x86_64 > nr_cpus : 160 > nr_nodes : 8 > cores_per_socket : 10 > threads_per_core : 2 > cpu_mhz : 2394 > hw_caps : > bfebfbff:2c100800:00000000:00003f40:02bee3ff:00000000:00000001:00000000 > virt_caps : hvm hvm_directio > total_memory : 2097142 > free_memory : 2040108 > free_cpus : 0 > xen_major : 4 > xen_minor : 1 > xen_extra : .3OVM > xen_caps : xen-3.0-x86_64 xen-3.0-x86_32p hvm-3.0-x86_32 > hvm-3.0-x86_32p hvm-3.0-x86_64 > xen_scheduler : credit > xen_pagesize : 4096 > platform_params : virt_start=0xffff800000000000 > xen_changeset : unavailable > xen_commandline : dom0_mem=31390M no-bootscrub > cc_compiler : gcc version 4.1.2 20080704 (Red Hat 4.1.2-48) > cc_compile_by : mockbuild > cc_compile_domain : us.oracle.com > cc_compile_date : Fri Oct 19 21:34:08 PDT 2012 > xend_config_format : 4 > > # uname -a > Linux ovs-3f-9e-04 2.6.39-300.17.1.el5uek #1 SMP Fri Oct 19 11:30:08 PDT > 2012 x86_64 x86_64 x86_64 GNU/Linux > > # cat /boot/grub/grub.conf > ... > kernel /xen.gz dom0_mem=31390M no-bootscrub dom0_vcpus_pin > dom0_max_vcpus=32 > > Test environment new: old env + cs 26056 > > Test script: test-vm-memory-allocation.sh (attached) > > My conclusion from the test: > > - HVM create time is greatly reduced. > - PVM create time is increased dramatically for 4G, 8G, 16G, 32G, 64G, 128G. > - HVM/PVM destroy time is not affected. > - If most of our customers are using PVM, I think this patch is bad: because > most VM memory should under 128G. > - If they are using HVM, then this patch is great. > > Questions for discussion: > > - Did you get the same result? > - It seems this result is not ideal. We may need to improve it. > > Please note: Imay not have access to the same machine for awhile. > > Thanks, > > Zhigang > _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
|
Lists.xenproject.org is hosted with RackSpace, monitoring our |