That's fine -- distraction is pretty much what defines my work... ;)
D.
On Tue, Dec 18, 2018 at 11:19 AM Jerven Tjalling Bolleman
wrote:
>
> Hi Dawid,
>
> Thanks for looking into this! I have been distracted with other work and
> did not get the time I expected to work on it.
>
> Regards,
> Jerven
> On 11/30/18 12:01 PM, Dawid Weiss wrote:
> > Just FYI: I implemented a quick and dirty PoC to see what it'd work
> > like. Not much of a difference on my machine (since postings merging
> > dominates everything else). Interesting problem how to split it up to
> > saturate all of available resources though (CPU and I/O).
> >
> > https://issues.apache.org/jira/browse/LUCENE-8580
> >
> > Dawid
> >
> > On Fri, Nov 2, 2018 at 10:17 PM Dawid Weiss wrote:
> >>
> >> Thanks for chipping in, Toke. A ~1TB index is impressive.
> >>
> >> Back of the envelope says reading & writing 900GB in 8 hours is
> >> 2*900GB/(8*60*60s) = 64MB/s. I don't remember the interface for our
> >> SSD machine, but even with SATA II this is only ~1/5th of the possible
> >> fairly sequential IO throughput. So for us at least, NVMe drives are
> >> not needed to have single-threaded CPU as bottleneck.
> >>
> >> The mileage will vary depending on the CPU -- if it can merge the data
> >> from multiple files at ones fast enough then it may theoretically
> >> saturate the bandwidth... but I agree we also seem to be CPU bound on
> >> these N-to-1 merges, a regular SSD is enough.
> >>
> >>> And +1 to the issue BTW.
> >>
> >> I agree. Fine-grained granularity here would be a win even in the
> >> regular "merge is a low-priority citizen" case. At least that's what I
> >> tend to think. And if there are spare CPUs, the gain would be
> >> terrific.
> >>
> >> Dawid
> >
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