From 083d012a388e7e2a8bfd9144c2c9bcceb29a78fc Mon Sep 17 00:00:00 2001 From: Richard Henderson Date: Mon, 29 Aug 2016 11:46:17 -0700 Subject: cutils: Add generic prefetch There's no real knowledge of the cacheline size, just prefetching one loop ahead. Signed-off-by: Richard Henderson Message-Id: <1472496380-19706-7-git-send-email-rth@twiddle.net> Signed-off-by: Paolo Bonzini --- util/bufferiszero.c | 5 +++++ 1 file changed, 5 insertions(+) (limited to 'util/bufferiszero.c') diff --git a/util/bufferiszero.c b/util/bufferiszero.c index bafd3d159c..abe65f9d88 100644 --- a/util/bufferiszero.c +++ b/util/bufferiszero.c @@ -38,6 +38,8 @@ static bool NAME(const void *buf, size_t len) \ do { \ const VECTYPE *p = buf; \ VECTYPE t; \ + __builtin_prefetch(buf + SIZE); \ + barrier(); \ if (SIZE == sizeof(VECTYPE) * 4) { \ t = (p[0] | p[1]) | (p[2] | p[3]); \ } else if (SIZE == sizeof(VECTYPE) * 8) { \ @@ -219,6 +221,9 @@ bool buffer_is_zero(const void *buf, size_t len) return true; } + /* Fetch the beginning of the buffer while we select the accelerator. */ + __builtin_prefetch(buf); + /* Use an optimized zero check if possible. Note that this also includes a check for an unrolled loop over 64-bit integers. */ return select_accel_fn(buf, len); -- cgit v1.2.1