[uae] Using more than 32MB of Zorro III memory and JIT direct-memory access on Linux
- From: Richard Drummond <evilrich@xxxxxxxxxxxxxx>
- To: uae@xxxxxxxxxxxxx
- Date: Mon, 9 May 2005 22:10:32 -0500
Hi All
Okay. As you may know, if you allocate more than 32 MB of Zorro III mem in
E-UAE, then the JIT's direct-memory allocation scheme fails (although on your
system the limit may actually be different) and performance is reduced.
I always thought this was a glibc limitation, but I was wrong. I guess I never
read the shmget man page very closely (JIT direct memory is allocated and
mapped using SYSV shared-memory calls).
Anyway, the limit on the size of a shmem segment is set by the kernel and it's
not a hard limit. It can be modified via the proc filesystem.
If you do
cat /proc/sys/kernel/shmmax
it should tell you the current maximum size of a shm segment in bytes (mine
was set to 33554432 which is 32 MB).
To change that, you need to be root. Simply echo the new size to
the /proc/sys/kernel/shmmax file.
For example, to set it to 64 MB, do
echo 67108864 > /proc/sys/kernel/shmmax
Cheers,
Rich
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