From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:51979) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bcPfA-0007IB-LW for qemu-devel@nongnu.org; Wed, 24 Aug 2016 00:19:41 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1bcPf8-0004fO-DO for qemu-devel@nongnu.org; Wed, 24 Aug 2016 00:19:39 -0400 Sender: Richard Henderson From: Richard Henderson Date: Tue, 23 Aug 2016 21:17:56 -0700 Message-Id: <1472012279-20581-5-git-send-email-rth@twiddle.net> In-Reply-To: <1472012279-20581-1-git-send-email-rth@twiddle.net> References: <1472012279-20581-1-git-send-email-rth@twiddle.net> Subject: [Qemu-devel] [PATCH 4/7] cutils: Add generic prefetch List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: vijay.kilari@gmail.com, qemu-arm@nongnu.org, pbonzini@redhat.com, peter.maydell@linaro.org There's no real knowledge of the cacheline size, just prefetching one loop ahead. Signed-off-by: Richard Henderson --- util/cutils.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/util/cutils.c b/util/cutils.c index 4d2edd6..0f1ce1d 100644 --- a/util/cutils.c +++ b/util/cutils.c @@ -173,6 +173,8 @@ 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) { \ @@ -376,6 +378,9 @@ 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 longs, as well as the unsized, unaligned fallback to buffer_zero_base. */ -- 2.7.4