Messages in this thread | | | Date | Mon, 6 Oct 1997 22:54:10 -0400 (EDT) | From | Benjamin LaHaise <> | Subject | Re: Large shared memory |
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On Mon, 6 Oct 1997, greg wrote:
> Hi all, > > In the kernel include file include/asm/shmparam.h SHMMAX is set to > 16MB (0x1000000) and I was wondering if it would be a bad thing to > set it to 64MB (0x4000000) or 128MB (0x8000000) provided the machine > in question had 64MB+ or 128MB+ memory.
In theory, increasing SHMMAX to 128MB should be possible... Beyond that, not without difficulty - the mm subsystem uses 128MB swap areas, of which shared memory is one.
> The purpose is I've implemented my own database and it needs to share > large amounts of memory; 64MB may not be enough but it'd be a good > start. The ideal machine for this database would have 128MB+ which my > test machine has and to keep the data off the disk once loaded.
Another alternative that will work with both 2.0.x and the future is to use shared mmap()ing of a file - that way you don't need to rely on users to tweak their kernel. Making use of the mmap()ed region to perform i/o could also net you a performance win...
-ben
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