git: 6260bfb08742 - main - powerpc: Optimize copyinstr() to avoid repeatedly mapping user strings

[Piotr Kubaj]

The branch main has been updated by pkubaj (ports committer):

URL: https://cgit.FreeBSD.org/src/commit/?id=6260bfb0874280d3fb58ac52699e2aee6ecca8a8

commit 6260bfb0874280d3fb58ac52699e2aee6ecca8a8
Author:     Justin Hibbits <chmeeedalf at gmail.com>
AuthorDate: 2020-06-04 18:15:15 +0000
Commit:     Piotr Kubaj <pkubaj at FreeBSD.org>
CommitDate: 2020-12-30 22:45:35 +0000

    powerpc: Optimize copyinstr() to avoid repeatedly mapping user strings
    
    Currently copyinstr() uses fubyte() to read each byte from userspace.
    However, this means that for each byte, it calls pmap_map_user_ptr() to
    map the string into memory.  This is needlessly wasteful, since the
    string will rarely ever cross a segment boundary.  Instead, map a
    segment at a time, and copy as much from that segment as possible at a
    time.
    
    Measured with the HPT pmap on powerpc64, this saves roughly 8% time on
    buildkernel, and 5% on buildworld, in wallclock time.
---
 sys/powerpc/powerpc/copyinout.c | 46 +++++++++++++++++++++++++++++------------
 1 file changed, 33 insertions(+), 13 deletions(-)

diff --git a/sys/powerpc/powerpc/copyinout.c b/sys/powerpc/powerpc/copyinout.c
index 76965ad996b8..1528accc0e0e 100644
--- a/sys/powerpc/powerpc/copyinout.c
+++ b/sys/powerpc/powerpc/copyinout.c
@@ -236,31 +236,51 @@ REMAP(copyin)(const void *udaddr, void *kaddr, size_t len)
 int
 REMAP(copyinstr)(const void *udaddr, void *kaddr, size_t len, size_t *done)
 {
+	struct		thread *td;
+	pmap_t		pm;
+	jmp_buf		env;
 	const char	*up;
-	char		*kp;
-	size_t		l;
-	int		rv, c;
+	char		*kp, *p;
+	size_t		i, l, t;
+	int		rv;
 
-	kp = kaddr;
-	up = udaddr;
+	td = curthread;
+	pm = &td->td_proc->p_vmspace->vm_pmap;
 
+	t = 0;
 	rv = ENAMETOOLONG;
 
-	for (l = 0; len-- > 0; l++) {
-		if ((c = fubyte(up++)) < 0) {
+	td->td_pcb->pcb_onfault = &env;
+	if (setjmp(env)) {
+		rv = EFAULT;
+		goto done;
+	}
+
+	kp = kaddr;
+	up = udaddr;
+
+	while (len > 0) {
+		if (pmap_map_user_ptr(pm, up, (void **)&p, len, &l)) {
 			rv = EFAULT;
-			break;
+			goto done;
 		}
 
-		if (!(*kp++ = c)) {
-			l++;
-			rv = 0;
-			break;
+		for (i = 0; len > 0 && i < l; i++, t++, len--) {
+			if ((*kp++ = *p++) == 0) {
+				i++, t++;
+				rv = 0;
+				goto done;
+			}
 		}
+
+		up += l;
 	}
 
+done:
+	td->td_pcb->pcb_onfault = NULL;
+
 	if (done != NULL) {
-		*done = l;
+		*done = t;
 	}
 
 	return (rv);