Sorry, not portable, but POSIX_FADV_WILLNEED is which can be used with posix_fadvise.
On Tue, Jun 16, 2009 at 8:12 PM, Jason Rutherglen < jason.rutherg...@gmail.com> wrote: > Perhaps we'd also like to request readahead be included in JDK7? > > http://linux.die.net/man/2/readahead > > On Tue, Jun 16, 2009 at 9:03 AM, Michael McCandless < > luc...@mikemccandless.com> wrote: > >> Hmm... posix_fadvise lets you do this with a file descriptor; this >> would be better for Lucene (per descriptor not per mapped region of >> RAM) since we could "advise" independent of which FSDir impl is in >> use... >> >> Mike >> >> On Tue, Jun 16, 2009 at 10:32 AM, Uwe Schindler<u...@thetaphi.de> wrote: >> > But to use it, we should change MMapDirectory to also use the mapping >> when >> > writing to files. I thought about it, it is very simple to implement >> (just >> > copy the IndexInput and change all gets() to sets()) >> > >> > ----- >> > Uwe Schindler >> > H.-H.-Meier-Allee 63, D-28213 Bremen >> > http://www.thetaphi.de >> > eMail: u...@thetaphi.de >> > >> >> -----Original Message----- >> >> From: Michael McCandless [mailto:luc...@mikemccandless.com] >> >> Sent: Tuesday, June 16, 2009 4:22 PM >> >> To: java-dev@lucene.apache.org >> >> Cc: Alan Bateman; nio-disc...@openjdk.java.net >> >> Subject: Re: madvise(ptr, len, MADV_SEQUENTIAL) >> >> >> >> Lucene could really make use of this method. When a segment merge >> >> takes place, we can read & write many GB of data, which without >> >> madvise on many OSs would effectively flush the IO cache (thus hurting >> >> our search performance). >> >> >> >> Mike >> >> >> >> On Mon, Jun 15, 2009 at 6:01 PM, Jason >> >> Rutherglen<jason.rutherg...@gmail.com> wrote: >> >> > Thanks Alan. >> >> > >> >> > I cross posted this to the Lucene dev list where we are discussing >> using >> >> > madvise for minimizing unnecessary IO cache usage when merging >> segments >> >> > (where we really want the newly merged segments in the IO cache >> rather >> >> than >> >> > the old segment files). >> >> > >> >> > How would the advise method work? Would there need to be a hint in >> the >> >> > FileChannel.map method? >> >> > >> >> > -J >> >> > >> >> > On Mon, Jun 15, 2009 at 12:36 AM, Alan Bateman <alan.bate...@sun.com >> > >> >> wrote: >> >> >> >> >> >> Jason Rutherglen wrote: >> >> >>> >> >> >>> Is there going to be a way to do this in the new Java IO APIs? >> >> >> >> >> >> Good question, as it has come up a few times and is needed for some >> >> >> important use-cases. A while back I looked into adding a >> >> >> MappedByteBuffer#advise method to allow the application provide >> hints >> >> on the >> >> >> expected usage but didn't complete it. We should probably look at >> this >> >> again >> >> >> for jdk7. >> >> >> >> >> >> -Alan. >> >> >> >> >> > >> >> > >> >> >> >> --------------------------------------------------------------------- >> >> To unsubscribe, e-mail: java-dev-unsubscr...@lucene.apache.org >> >> For additional commands, e-mail: java-dev-h...@lucene.apache.org >> > >> > >> > >> > --------------------------------------------------------------------- >> > To unsubscribe, e-mail: java-dev-unsubscr...@lucene.apache.org >> > For additional commands, e-mail: java-dev-h...@lucene.apache.org >> > >> > >> >> --------------------------------------------------------------------- >> To unsubscribe, e-mail: java-dev-unsubscr...@lucene.apache.org >> For additional commands, e-mail: java-dev-h...@lucene.apache.org >> >> >
