would be better to document it first on "Known system-wise tuning knobs" in the doc? 2017-05-05 8:28 GMT+08:00 Brad Hubbard <bhubbard@xxxxxxxxxx>: > 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 > -- > To unsubscribe from this list: send the line "unsubscribe ceph-devel" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe ceph-devel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
