Messages in this thread | | | Date | Sat, 11 Apr 1998 15:11:04 -0400 (EDT) | From | <> | Subject | Re: bigphysarea in 2.2 |
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I'de also like to suggest someone put in the option of hard allocating DMA bufferspace at the kernel command line..
I've got enough RAM that I wouldn't mind giving up 512k at boot just so that I *know* that there will be ram available for my soundcard, ftape, floppy, isa nic, etc.. (ok ok I only have a soundcard in this box, but I used to use FTAPE.. youck)...
On Sat, 11 Apr 1998, Stephen Williams wrote:
> > I deal with some high-performance image processing hardware. I work in > gray a lot, and a 200DPI high-speed color scanner is soon to come to > reality. That said... > > David.Mentre@irisa.fr said: > > With the new kernel memory manager, and if the defragmenting code > > which is under development works, wouldn't it be more useful to use > > standard kernel memory allocation. Static allocation like in > > bigphysarea is more a work-around that a real solution. > > It is common for me to need many megabytes per board. In most cases > they are perfectly capable of scatter-gather, but the huge volume, even > broken into 4K pages, is usually hard to get, especially after the system > has been running for a while. (Think loadable modules.) > > I do occasionally run into boards that do *not* do scatter-gather, and > they require lots of contiguous memory. These are typically not high > quantity, and so not worth the effort of fancy DMA controllers. > > It actually strikes me as a bad idea to try to make a memory manager > that handles these extreme cases at the expense of the normal case. The > bigphysarea patch offers a different memory allocator intended for doing > only a few allocations in a big space. This way it doesn't get in the > way or needlessly complicate the normal allocator. It can also be > practically turned off without recompiling the kernel. > > I think it is reasonable to expect my customers of such extreme hardware > to set aside memory specifically for the board so that such allocation > doesn't over-tax the normal allocation mechanism. Putting bigphysarea=foo > in /etc/lilo.conf is not too much to ask, patching the kernel source or > restricting them to a specific kernel version, well... > > I believe that the bigphysarea patch is worth making a part of the kernel > as a whole because the Linux kernel is very well suited to these extreme > tasks that occasionally have special memory requirements. The bigphysarea > support is simple, yes, and it helps *a lot*. > > (The patch can also be modified to put to good use that non-cached memory > that some computers seem to have.) > > > -- > Steve Williams "The woods are lovely, dark and deep. > steve@icarus.com But I have promises to keep, > steve@picturel.com and lines to code before I sleep, > http://www.picturel.com And lines to code before I sleep." > > > > - > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.rutgers.edu >
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