kernel - Don't call lwkt_user_yield() in uiomove() unless xfer is big

* Only call lwkt_user_yield() in uiomove() when the xfer is big.

diff --git a/sys/kern/kern_subr.c b/sys/kern/kern_subr.c
index a6f6f55..a4c9502 100644 (file)
--- a/sys/kern/kern_subr.c
+++ b/sys/kern/kern_subr.c
@@ -78,6 +78,7 @@ uiomove(caddr_t cp, size_t n, struct uio *uio)
        thread_t td = curthread;
        struct iovec *iov;
        size_t cnt;
+       size_t tot;
        int error = 0;
        int save = 0;
 
@@ -91,6 +92,8 @@ uiomove(caddr_t cp, size_t n, struct uio *uio)
        td->td_flags |= TDF_DEADLKTREAT;
        crit_exit();
 
+       tot = 0;
+
        while (n > 0 && uio->uio_resid) {
                iov = uio->uio_iov;
                cnt = iov->iov_len;
@@ -101,11 +104,12 @@ uiomove(caddr_t cp, size_t n, struct uio *uio)
                }
                if (cnt > n)
                        cnt = n;
+               tot += cnt;
 
                switch (uio->uio_segflg) {
-
                case UIO_USERSPACE:
-                       lwkt_user_yield();
+                       if (tot > 1024*1024)
+                               lwkt_user_yield();
                        if (uio->uio_rw == UIO_READ)
                                error = copyout(cp, iov->iov_base, cnt);
                        else