Interesting. Never came up in my profiling of raw scan performance. Of course my assumption was that the vast majority of all KVs are in HFiles and thus in the blockcache (not the memstore).
ThreadLocals are indeed expensive, we ran into such problems as well (code unrelated to HBase, though). Mind filing a jira, Vladimir? If there's a perf issue, we should fix it. -- Lars ________________________________ From: Vladimir Rodionov <[email protected]> To: "[email protected]" <[email protected]> Sent: Friday, October 11, 2013 2:36 PM Subject: Re: skipKVsNewerThanReadpoint in StoreFileScanner and MemStoreScanner Yes, threadLocal.get() is expensive when you count every nanosecond. There is no need to call it every time in MemStoreScanner.next(). On Fri, Oct 11, 2013 at 2:32 PM, Ted Yu <[email protected]> wrote: > MultiVersionConsistencyControl.getThreadReadPoint() retrieves value from a > ThreadLocal. > > Can you specify which operation becomes expensive ? > > BTW I only found IsolationLevel.READ_UNCOMMITTED > in TestRowProcessorEndpoint. Looks like it is not normally used. > > > On Fri, Oct 11, 2013 at 2:20 PM, Vladimir Rodionov > <[email protected]>wrote: > > > Update. > > > > This method is not called in MemStoreScanner, but direct call to : > > > > readPoint = MultiVersionConsistencyControl.getThreadReadPoint(); > > > > on every next, seek etc > > which is basically the same. > > > > All these calls become very expensive when you try to achieve 10s of > > millions RPS in scan operations. > > > > Best regards, > > Vladimir Rodionov > > Principal Platform Engineer > > Carrier IQ, www.carrieriq.com > > e-mail: [email protected] > > > > ________________________________________ > > From: Vladimir Rodionov > > Sent: Friday, October 11, 2013 2:18 PM > > To: [email protected] > > Subject: skipKVsNewerThanReadpoint in StoreFileScanner and > MemStoreScanner > > > > From HRegion: > > > > synchronized(scannerReadPoints) { > > if (isolationLevel == IsolationLevel.READ_UNCOMMITTED) { > > // This scan can read even uncommitted transactions > > this.readPt = Long.MAX_VALUE; > > MultiVersionConsistencyControl.setThreadReadPoint(this.readPt); > > } else { > > this.readPt = > > MultiVersionConsistencyControl.resetThreadReadPoint(mvcc); > > } > > > > If isolation level is READ_UNCOMMITTED than this method should never be > > called in both StoreFileScanner and MemStoreScanner > > If isolation level is READ_COMMITTED than this method must be called only > > in MemStoreScanner, because HFiles are immutable no new KV's can be added > > to HFile after StoreFileScanner was created. > > > > > > Correct? > > > > > > Best regards, > > Vladimir Rodionov > > Principal Platform Engineer > > Carrier IQ, www.carrieriq.com > > e-mail: [email protected] > > > > Confidentiality Notice: The information contained in this message, > > including any attachments hereto, may be confidential and is intended to > be > > read only by the individual or entity to whom this message is addressed. > If > > the reader of this message is not the intended recipient or an agent or > > designee of the intended recipient, please note that any review, use, > > disclosure or distribution of this message or its attachments, in any > form, > > is strictly prohibited. If you have received this message in error, > please > > immediately notify the sender and/or [email protected] and > > delete or destroy any copy of this message and its attachments. > > >
