Messages in this thread | | | Date | Tue, 13 Jun 2006 14:16:00 -0700 | From | "Randy.Dunlap" <> | Subject | Re: Packing data in kernel memory |
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On Tue, 13 Jun 2006 16:54:26 -0400 John Richard Moser wrote:
> Randy.Dunlap wrote: > > On Tue, 13 Jun 2006 22:18:55 +0200 (MEST) Jan Engelhardt wrote: > > > >>> Subject: Packing data in kernel memory > >>> > >> Can't you just use mlock(), if you want to keep it in RAM? > >> > >> Or do you need it in kernel memory, because you need it in the lowmem area? > >> Or for interaction with other kernel code? > >> > >>> Is there a way to pack and store arbitrary data in the kernel, or do I > >>> need to roll my own? > > > > Sounds a bit like a slab cache to me. > > > > OK cool, can I make that non-swappable?
kernel (allocated) memory is non-swappable.
> I'm going to be trying to do > this between where kernel swaps a page out and swapped page actually is > written to disk. The result will be a "Swap Zone," in-memory storage of > pages that the rest of the kernel thinks have been swapped to disk. > (Code here will use the swap interface, so the rest of the kernel thinks > it's just swapping; I'll handle whether to pull it out of memory or off > disk behind that) > > The need for packing pages comes because eventually (using above > infrastructure) I'll be taking sets of 32KiB of data and compressing it; > I don't want to pad up to 4095 excess unused bytes if that stuff > compresses to 28KiB+1 :) (more likely 16KiB+1 +/-8KiB) > > This is all, of course, assuming I ever figure out how the heck to get > in the middle of the swapping process. I'm looking at mm/page_io.c > swap_writepage() and friends and scratching my head. I have no idea wtf... > > > >> Write a device driver, kmalloc some buffer, and copy data via a write > >> function from userspace to that buffer. Should be trivial. > >> > >>> 1 excess pages, 4 units wasted memory. > >> Of course, kmalloc only works up to some boundary AFIACS. > > > > 128 KB on some arches. More on a few IIRC.
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