On Thu, May 4, 2017 at 10:58 AM, Haomai Wang <haomai@xxxxxxxx> wrote: > refer to https://github.com/ceph/ceph/pull/5013 How about we issue a warning about possible performance implications if we detect this is not set to 1 *or* 0 at startup? > > On Thu, May 4, 2017 at 7:56 AM, Brad Hubbard <bhubbard@xxxxxxxxxx> wrote: >> +ceph-devel to get input on whether we want/need to check the value of >> /dev/cpu_dma_latency (platform dependant) at startup and issue a >> warning, or whether documenting this would suffice? >> >> Any doc contribution would be welcomed. >> >> On Wed, May 3, 2017 at 7:18 PM, Blair Bethwaite >> <blair.bethwaite@xxxxxxxxx> wrote: >>> On 3 May 2017 at 19:07, Dan van der Ster <dan@xxxxxxxxxxxxxx> wrote: >>>> Whether cpu_dma_latency should be 0 or 1, I'm not sure yet. I assume >>>> your 30% boost was when going from throughput-performance to >>>> dma_latency=0, right? I'm trying to understand what is the incremental >>>> improvement from 1 to 0. >>> >>> Probably minimal given that represents a state transition latency >>> taking only 1us. Presumably the main issue is when the CPU can drop >>> into the lower states and the compounding impact of that over time. I >>> will do some simple characterisation of that over the next couple of >>> weeks and report back... >>> >>> -- >>> Cheers, >>> ~Blairo >>> _______________________________________________ >>> ceph-users mailing list >>> ceph-users@xxxxxxxxxxxxxx >>> http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com >> >> >> >> -- >> Cheers, >> Brad >> _______________________________________________ >> ceph-users mailing list >> ceph-users@xxxxxxxxxxxxxx >> http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com -- Cheers, Brad _______________________________________________ ceph-users mailing list ceph-users@xxxxxxxxxxxxxx http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
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