Maybe what I was looking for was resources like this https://0xax.gitbooks.io/linux-insides/content.
On Sat, Feb 6, 2016 at 7:54 PM, Kristoffer Sjögren <[email protected]> wrote: > Ok, so the page cache, that's exactly what I want to read more about. > Not for tuning, but just to understand how the page cache works with > the different subsystems in order to dimension the hardware properly. > For example what IO devices affect the page cache? Why are memory > pages reshuffled between different NUMA nodes? etc.. > > On Sat, Feb 6, 2016 at 7:15 PM, Jay Booth <[email protected]> wrote: >> Mmapped memory goes through the exact same page cache as all other >> filesystem data -- you probably want to do exactly nothing for optimal >> performance, the kernel will be smart about what it keeps paged in >> >> On Sat, Feb 6, 2016 at 12:44 PM, Kristoffer Sjögren <[email protected]> >> wrote: >>> >>> I'm not looking for fairies :-) I was just curious exactly how mmap >>> interacts with the OS in order to understand performance metrics >>> better. >>> >>> On Sat, Feb 6, 2016 at 5:46 PM, Howard Chu <[email protected]> wrote: >>> > Kristoffer Sjögren wrote: >>> >> >>> >> Thanks Howard. What's the best documentation on mmap you know, aside >>> >> from read kernel source code? >>> > >>> > >>> > Not sure what you're asking. Read the mmap(2) manpage and its related >>> > pages. >>> > If you're thinking there's something fancy hidden in there for you to >>> > take >>> > advantage of, I don't think you should be using mmap in the first place. >>> > >>> > >>> >> On Fri, Feb 5, 2016 at 10:33 PM, Howard Chu <[email protected]> wrote: >>> >>> >>> >>> Kristoffer Sjögren wrote: >>> >>>> >>> >>>> >>> >>>> Hi >>> >>>> >>> >>>> Our application do lots of caching using vmtouch, up to a point where >>> >>>> there isn't a lot of memory left on the machine. We would like to use >>> >>>> LMDB on the same machine to store around 40GiB data of a few hundred >>> >>>> million entries. >>> >>>> >>> >>>> How can we best understand the interaction and behavior of the OS >>> >>>> cache and sharing of memory between processes? Is LMDB doing >>> >>>> something >>> >>>> to help the OS? >>> >>> >>> >>> >>> >>> >>> >>> Nope, LMDB does nothing special with its mmap. >>> >>> >>> >>> -- >>> >>> -- Howard Chu >>> >>> CTO, Symas Corp. http://www.symas.com >>> >>> Director, Highland Sun http://highlandsun.com/hyc/ >>> >>> Chief Architect, OpenLDAP http://www.openldap.org/project/ >>> >> >>> >> >>> > >>> > >>> > -- >>> > -- Howard Chu >>> > CTO, Symas Corp. http://www.symas.com >>> > Director, Highland Sun http://highlandsun.com/hyc/ >>> > Chief Architect, OpenLDAP http://www.openldap.org/project/ >>> >>
