On Mon, Nov 12, 2018 at 10:39 AM Vijay Bellur <[email protected]> wrote:
> > > On Sun, Nov 11, 2018 at 8:25 PM Raghavendra Gowdappa <[email protected]> > wrote: > >> >> >> On Sun, Nov 11, 2018 at 11:41 PM Vijay Bellur <[email protected]> wrote: >> >>> >>> >>> On Mon, Nov 5, 2018 at 8:31 PM Raghavendra Gowdappa <[email protected]> >>> wrote: >>> >>>> >>>> >>>> On Tue, Nov 6, 2018 at 9:58 AM Vijay Bellur <[email protected]> wrote: >>>> >>>>> >>>>> >>>>> On Mon, Nov 5, 2018 at 7:56 PM Raghavendra Gowdappa < >>>>> [email protected]> 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. Regards, Amar 3. Think of some other option? > > Thanks, > Vijay > > >> _______________________________________________ > Gluster-users mailing list > [email protected] > https://lists.gluster.org/mailman/listinfo/gluster-users -- Amar Tumballi (amarts)
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