Not sure if you are really stating the problem here. If you don't use Solr sharding, (I also assume you aren't using SolrCloud), and I'm guessing you are a single core (but can you confirm).
As I understand Solr's logic, for a single query on a single core, that will only use 1 thread (ignoring updates, background merges, etc). A Lucene index (with multiple segments) has each segment read sequentially, so a search must scan all the segments and that inherently is a single-threaded activity. The fact that the search uses less CPU is not really the issue (it might actually be a GOOD thing, it could mean the code is more efficient!), so I would consider that a red herring. The real issue is that the search takes longer in elapsed time. The usual questions apply: 1) how did you upgrade, did you port your config, or start from a fresh Solr 4 config and add your custom stuff to it. 2) Is your new index comparable to your old one, does it have more segments, how did you fill it (bulk import or upgrade of old 1.4.1 index), and what is your merge policy for the index? Upgrades from such an old version of Solr have been asked before on the list, the consensus is that you probably need to re-tune your configuration (starting with a Solr 4 basic config) since Solr 4 is so different under the hood from 1.x On 5 December 2013 09:11, Salman Akram <salman.ak...@northbaysolutions.net>wrote: > More info on Cpu consumption: We have a server with 32 physical cores. > > Same search when executed on SOLR 4.6 takes quite long and throughout only > uses 3% cpu (1 core). > > Same search when executed on SOLR 1.4.1 takes much less time and on average > uses around 40-50% cpu. > > > On Thu, Dec 5, 2013 at 2:05 PM, Salman Akram < > salman.ak...@northbaysolutions.net> wrote: > > > I missed one imp piece of info. Due to large size we have indexed the > date > > with Common Grams. All of the words in slow search are in common grams > and > > when I debug it, they query is made properly with common grams. > > > > In debug all of the time is shown in process query time. > > > > Let me know what other info you need? Thanks > > > > > > On Thu, Dec 5, 2013 at 11:38 AM, Andrea Gazzarini <agazzar...@apache.org > >wrote: > > > >> Hi, I did moreless the same but didn't get that behaviour...could you > give > >> us more details > >> > >> Best, > >> Gazza > >> On 5 Dec 2013 06:54, "Salman Akram" <salman.ak...@northbaysolutions.net > > > >> wrote: > >> > >> > Hi, > >> > > >> > We recently upgraded to SOLR 4.6 from SOLR 1.4.1. Overall the > >> performance > >> > went down for large phrase queries. On some analysis we have seen that > >> > 1.4.1 utilized multiple cpu cores for such queries but SOLR 4.6 is > only > >> > utilizing single cpu core. Any idea on what could be the reason? > >> > > >> > Note: We are not using SOLR Sharding. > >> > > >> > -- > >> > Regards, > >> > > >> > Salman Akram > >> > > >> > > > > > > > > -- > > Regards, > > > > Salman Akram > > > > > > > -- > Regards, > > Salman Akram >
