[PATCH] uml: TLB operation batching
This adds VM op batching to skas0. Rather than having a context switch to and
from the userspace stub for each address space change, we write a number of
operations to the stub data page and invoke a different stub which loops over
them and executes them all in one go.
The operations are stored as [ system call number, arg1, arg2, ... ] tuples.
The set is terminated by a system call number of 0. Single operations, i.e.
page faults, are handled in the old way, since that is slightly more
efficient.
For a kernel build, a minority (~1/4) of the operations are part of a set.
These sets averaged ~100 in length, so for this quarter, the context switching
overhead is greatly reduced.
Signed-off-by: Jeff Dike <jdike@addtoit.com>
Cc: Paolo Giarrusso <blaisorblade@yahoo.it>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/arch/um/sys-i386/stub.S b/arch/um/sys-i386/stub.S
index 2f2c70a..a0f9506 100644
--- a/arch/um/sys-i386/stub.S
+++ b/arch/um/sys-i386/stub.S
@@ -6,3 +6,20 @@
int $0x80
mov %eax, UML_CONFIG_STUB_DATA
int3
+
+ .globl batch_syscall_stub
+batch_syscall_stub:
+ mov $UML_CONFIG_STUB_DATA, %esp
+again: pop %eax
+ cmpl $0, %eax
+ jz done
+ pop %ebx
+ pop %ecx
+ pop %edx
+ pop %esi
+ pop %edi
+ pop %ebp
+ int $0x80
+ mov %eax, UML_CONFIG_STUB_DATA
+ jmp again
+done: int3