[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>

1 files changed, 14 insertions, 9 deletions

diff --git a/arch/um/kernel/skas/tlb.c b/arch/um/kernel/skas/tlb.c
index 6230999c672..4b5fd204954 100644
--- a/arch/um/kernel/skas/tlb.c
+++ b/arch/um/kernel/skas/tlb.c
@@ -18,7 +18,8 @@
 #include "os.h"
 #include "tlb.h"
 
-static void do_ops(union mm_context *mmu, struct host_vm_op *ops, int last)
+static void *do_ops(union mm_context *mmu, struct host_vm_op *ops, int last,
+		    int finished, void *flush)
 {
 	struct host_vm_op *op;
 	int i;
@@ -27,24 +28,28 @@ static void do_ops(union mm_context *mmu, struct host_vm_op *ops, int last)
 		op = &ops[i];
 		switch(op->type){
 		case MMAP:
-                        map(&mmu->skas.id, op->u.mmap.addr, op->u.mmap.len,
-			    op->u.mmap.r, op->u.mmap.w, op->u.mmap.x,
-			    op->u.mmap.fd, op->u.mmap.offset);
+			flush = map(&mmu->skas.id, op->u.mmap.addr,
+				    op->u.mmap.len, op->u.mmap.r, op->u.mmap.w,
+				    op->u.mmap.x, op->u.mmap.fd,
+				    op->u.mmap.offset, finished, flush);
 			break;
 		case MUNMAP:
-                        unmap(&mmu->skas.id, (void *) op->u.munmap.addr,
-			      op->u.munmap.len);
+			flush = unmap(&mmu->skas.id, (void *) op->u.munmap.addr,
+				      op->u.munmap.len, finished, flush);
 			break;
 		case MPROTECT:
-                        protect(&mmu->skas.id, op->u.mprotect.addr,
-                                op->u.mprotect.len, op->u.mprotect.r,
-                                op->u.mprotect.w, op->u.mprotect.x);
+			flush = protect(&mmu->skas.id, op->u.mprotect.addr,
+					op->u.mprotect.len, op->u.mprotect.r,
+					op->u.mprotect.w, op->u.mprotect.x,
+					finished, flush);
 			break;
 		default:
 			printk("Unknown op type %d in do_ops\n", op->type);
 			break;
 		}
 	}
+
+	return flush;
 }
 
 extern int proc_mm;