The documentation goes on the conservative side of the recommendation. It says for "UNIX systems, swap space at least equal to the amount of physical memory on the machine. Swap space equal to twice the amount of physical memory is highly recommended." And when it mentions the Huge page subtraction, it uses the more conservative 2x - Huge pages.
The swap space ensures that the operating system can allocate very large chunks of memory *without needing to use the swap space*. It seems counter-intuitive, but it is good (and cheap) insurance to keep your performance at its peak, even when big chunks of memory are asked for. -Danny -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of David Sewell Sent: Thursday, May 24, 2012 10:04 AM To: MarkLogic Developer Discussion Subject: Re: [MarkLogic Dev General] MarkLogic and swap space on Linux On Thu, 24 May 2012, Hsiao Su wrote: > Brent and David Lee's comments are correct. > > Back to the original question, if you do have 64 GB of physical memory, and > 24 > GB are allocated to huge pages, then you would only need 64 - 24 = 40 GB of > swap space. This is because huge pages are never swapped. Hmm, the MarkLogic "Installation Guide for All Platforms" doc says: "If you have Huge Pages set up on a Linux system, your swap space on that machine should be twice the size of your physical memory minus the size of your Huge Page" or (64 * 24) * 2 = 80. So that's what I was going by. Thanks, all, for the input. David > If you do have to add more swap space for any reason, there is no particular > preference whether it's a partition or a swap file. > > Hsiao "Shao" Su > Senior Performance Engineer > MarkLogic Corporation > [email protected] > Phone: +1 650 287 2545 > www.marklogic.com > > This e-mail and any accompanying attachments are confidential. The > information is intended solely for the use of the individual to whom it is > addressed. Any review, disclosure, copying, distribution, or use of this > e-mail communication by others is strictly prohibited. If you are not the > intended recipient, please notify us immediately by returning this message to > the sender and delete all copies. Thank you for your cooperation. > > > > -----Original Message----- > From: [email protected] > [mailto:[email protected]] On Behalf Of Brent Hartwig > Sent: Thursday, May 24, 2012 9:13 AM > To: MarkLogic Developer Discussion > Subject: Re: [MarkLogic Dev General] MarkLogic and swap space on Linux > > Agreed. I understand swap space should be allocated to the ML process as a > contingency, as Linux will kill the process if it runs out of memory. It > provides time for administrators to figure out what is going on, before there > is a failure. > > -----Original Message----- > From: [email protected] > [mailto:[email protected]] On Behalf Of David Lee > Sent: Thursday, May 24, 2012 12:10 PM > To: MarkLogic Developer Discussion > Subject: Re: [MarkLogic Dev General] MarkLogic and swap space on Linux > > I'm not authorative on this, but ML is designed to run best *without* > swapping so it probably doesnt matter at all how you setup your swap space. > If ML starts swapping at all it will run dog slow, so if it were me I'd just > keep an eye on the swap space and see if you even need to add more, most > likely your 64GB of swap partition is hardly touched. > > > ----------------------------------------------------------------------------- > David Lee > Lead Engineer > MarkLogic Corporation > [email protected] > Phone: +1 650-287-2531 > Cell: +1 812-630-7622 > www.marklogic.com > > This e-mail and any accompanying attachments are confidential. The > information is intended solely for the use of the individual to whom it is > addressed. Any review, disclosure, copying, distribution, or use of this > e-mail communication by others is strictly prohibited. If you are not the > intended recipient, please notify us immediately by returning this message to > the sender and delete all copies. Thank you for your cooperation. > > >> -----Original Message----- >> From: [email protected] [mailto:general- >> [email protected]] On Behalf Of David Sewell >> Sent: Thursday, May 24, 2012 11:20 AM >> To: General Mark Logic Developer Discussion >> Subject: [MarkLogic Dev General] MarkLogic and swap space on Linux >> >> I've got an installation of MarkLogic 5 on a (single server) RHEL 6 >> machine. It has 64 GB physical memory and a 64 GB swap partition. >> Ideally per MarkLogic installation specs it should have 80 GB swap >> (plus 24 GB in Huge Pages). Easiest way to increase swap space would >> be to add a swap file, but I'm wondering if the way MarkLogic uses >> memory makes it desireable to have contiguous swap space on a >> dedicated partition. >> >> DS >> >> -- >> David Sewell, Editorial and Technical Manager ROTUNDA, The University >> of Virginia Press PO Box 400314, Charlottesville, VA 22904-4314 USA >> Email: [email protected] Tel: +1 434 924 9973 >> Web: http://rotunda.upress.virginia.edu/ >> _______________________________________________ >> General mailing list >> [email protected] >> http://community.marklogic.com/mailman/listinfo/general > _______________________________________________ > General mailing list > [email protected] > http://community.marklogic.com/mailman/listinfo/general > _______________________________________________ > General mailing list > [email protected] > http://community.marklogic.com/mailman/listinfo/general > _______________________________________________ > General mailing list > [email protected] > http://community.marklogic.com/mailman/listinfo/general > -- David Sewell, Editorial and Technical Manager ROTUNDA, The University of Virginia Press PO Box 400314, Charlottesville, VA 22904-4314 USA Email: [email protected] Tel: +1 434 924 9973 Web: http://rotunda.upress.virginia.edu/ _______________________________________________ General mailing list [email protected] http://community.marklogic.com/mailman/listinfo/general _______________________________________________ General mailing list [email protected] http://community.marklogic.com/mailman/listinfo/general
