On Tue, 2013-08-20 at 17:22 -0400, Mikulas Patocka wrote: > On Fri, 16 Aug 2013, Frank Mayhar wrote: > > The device mapper and some of its modules allocate memory pools at > > various points when setting up a device. In some cases, these pools are > > fairly large, for example the multipath module allocates a 256-entry > > pool and the dm itself allocates three of that size. In a > > memory-constrained environment where we're creating a lot of these > > devices, the memory use can quickly become significant. Unfortunately, > > there's currently no way to change the size of the pools other than by > > changing a constant and rebuilding the kernel. > I think it would be better to set the values to some low value (1 should > be enough, there is 16 in some places that is already low enough). There > is no need to make it user-configurable, because the user will see no > additional benefit from bigger mempools. > > Maybe multipath is the exception - but other dm targets don't really need > big mempools so there is no need to make the size configurable. The point is not to make the mempools bigger, the point is to be able to make them _smaller_ for memory-constrained environments. In some cases, even 16 can be too big, especially when creating a large number of devices. In any event, it seems unfortunate to me that these values are hard-coded. One shouldn't have to rebuild the kernel to change them, IMHO. -- Frank Mayhar 310-460-4042 -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
