On Mon, Nov 12, 2018 at 10:48 AM Amar Tumballi <atumb...@redhat.com> wrote:
> > > On Mon, Nov 12, 2018 at 10:39 AM Vijay Bellur <vbel...@redhat.com> wrote: > >> >> >> On Sun, Nov 11, 2018 at 8:25 PM Raghavendra Gowdappa <rgowd...@redhat.com> >> wrote: >> >>> >>> >>> On Sun, Nov 11, 2018 at 11:41 PM Vijay Bellur <vbel...@redhat.com> >>> wrote: >>> >>>> >>>> >>>> On Mon, Nov 5, 2018 at 8:31 PM Raghavendra Gowdappa < >>>> rgowd...@redhat.com> wrote: >>>> >>>>> >>>>> >>>>> On Tue, Nov 6, 2018 at 9:58 AM Vijay Bellur <vbel...@redhat.com> >>>>> wrote: >>>>> >>>>>> >>>>>> >>>>>> On Mon, Nov 5, 2018 at 7:56 PM Raghavendra Gowdappa < >>>>>> rgowd...@redhat.com> wrote: >>>>>> >>>>>>> All, >>>>>>> >>>>>>> There is a patch [1] from Kotresh, which makes ctime generator as >>>>>>> default in stack. Currently ctime generator is being recommended only >>>>>>> for >>>>>>> usecases where ctime is important (like for Elasticsearch). However, a >>>>>>> reliable (c)(m)time can fix many consistency issues within glusterfs >>>>>>> stack >>>>>>> too. These are issues with caching layers having stale (meta)data >>>>>>> [2][3][4]. Basically just like applications, components within glusterfs >>>>>>> stack too need a time to find out which among racing ops (like write, >>>>>>> stat, >>>>>>> etc) has latest (meta)data. >>>>>>> >>>>>>> Also note that a consistent (c)(m)time is not an optional feature, >>>>>>> but instead forms the core of the infrastructure. So, I am proposing to >>>>>>> merge this patch. If you've any objections, please voice out before Nov >>>>>>> 13, >>>>>>> 2018 (a week from today). >>>>>>> >>>>>>> As to the existing known issues/limitations with ctime generator, my >>>>>>> conversations with Kotresh, revealed following: >>>>>>> * Potential performance degradation (we don't yet have data to >>>>>>> conclusively prove it, preliminary basic tests from Kotresh didn't >>>>>>> indicate >>>>>>> a significant perf drop). >>>>>>> >>>>>> >>>>>> Do we have this data captured somewhere? If not, would it be possible >>>>>> to share that data here? >>>>>> >>>>> >>>>> I misquoted Kotresh. He had measured impact of gfid2path and said both >>>>> features might've similar impact as major perf cost is related to storing >>>>> xattrs on backend fs. I am in the process of getting a fresh set of >>>>> numbers. Will post those numbers when available. >>>>> >>>>> >>>> >>>> I observe that the patch under discussion has been merged now [1]. A >>>> quick search did not yield me any performance data. Do we have the >>>> performance numbers posted somewhere? >>>> >>> >>> No. Perf benchmarking is a task pending on me. >>> >> >> When can we expect this task to be complete? >> >> In any case, I don't think it is ideal for us to merge a patch without >> completing our due diligence on it. How do we want to handle this scenario >> since the patch is already merged? >> >> We could: >> >> 1. Revert the patch now >> 2. Review the performance data and revert the patch if performance >> characterization indicates a significant dip. It would be preferable to >> complete this activity before we branch off for the next release. >> > > I am for option 2. Considering the branch out for next release is another > 2 months, and no one is expected to use the 'release' off a master branch > yet, it makes sense to give that buffer time to get this activity completed. > Its unlikely I'll have time for carrying out perf benchmark. Hence I've posted a revert here: https://review.gluster.org/#/c/glusterfs/+/21975/ > Regards, > Amar > > 3. Think of some other option? >> >> Thanks, >> Vijay >> >> >>> _______________________________________________ >> Gluster-users mailing list >> gluster-us...@gluster.org >> https://lists.gluster.org/mailman/listinfo/gluster-users > > > > -- > Amar Tumballi (amarts) >
_______________________________________________ Gluster-devel mailing list Gluster-devel@gluster.org https://lists.gluster.org/mailman/listinfo/gluster-devel
