On Mon, Dec 16, 2013 at 04:21:28PM +0100, Antonios Motakis wrote: > On Mon, Dec 16, 2013 at 8:32 AM, Edgar E. Iglesias > <edgar.igles...@gmail.com> wrote: > > On Fri, Dec 13, 2013 at 12:14:31PM +0100, Antonios Motakis wrote: > > This option complements -mem-path. It implies -mem-prealloc. If > specified, > > the guest RAM is allocated as a shared memory object. If both > -mem-path > > and -mem-share are provided, the memory is allocated from the > HugeTLBFS > > supplied path, and then mmapped with MAP_SHARED. > > Hi, > > Interesting, I've got a similar use-case here where I've added a > -mem-shared > option. I've got a few comments/questions. > > Why do you imply -mem-prealloc? cant the user keep controlling that > through > -mem-prealloc? > > I'd prefer if -mem-share did not use shm_open but took a directory path > as arg > and created the backing files there. I'd also prefer if the files had > deterministic names and where not unlinked after creation. I.e, let the > user > delete them when no longer needed. > > The reason for this is that it makes it easier to use apps that are not > aware of shm or QEMU specifics to manipulate the memory backing. I > understand > that there might be issues (e.g filling up the disk, slow access over > NFS etc) > but these are at the choice of the user. > > Currently -mem-path implies HugeTLBFS for the supplied path. Maybe we > should change > its behavior to do what you suggest: > > -mem-path - specify a directory where to allocate the mmap-ed ram files > (and don't unlink them) > -mem-hugetlbfs - check mem-path directory for HugeTLBFS (do we need this > one?) > -mem-share - add MAP_SHARED to mmap > -mem-prealloc - preallocate the memory > How does this sound?
It sounds good to me, but I'm not sure its a good thing to change the behaviour of -mem-path and break backwards compatibility. Maybe we could relax the hugetlbfs impl for -mem-path in that it uses it the huge page sizes if the underlying fs is hugetlbfs and otherwise not? In my local implementation mem-share takes an argument by itself and replaces the need for -mem-path, not very intuitive I agree but its an alternative. Cheers, Edgar
