From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:51032) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ebS4j-0003kO-8f for qemu-devel@nongnu.org; Tue, 16 Jan 2018 09:18:55 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ebS4e-0005Ud-Fa for qemu-devel@nongnu.org; Tue, 16 Jan 2018 09:18:53 -0500 Received: from mail-wm0-x242.google.com ([2a00:1450:400c:c09::242]:34837) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_128_CBC_SHA1:16) (Exim 4.71) (envelope-from ) id 1ebS4e-0005Tv-8m for qemu-devel@nongnu.org; Tue, 16 Jan 2018 09:18:48 -0500 Received: by mail-wm0-x242.google.com with SMTP id r78so9011779wme.0 for ; Tue, 16 Jan 2018 06:18:48 -0800 (PST) Sender: Paolo Bonzini From: Paolo Bonzini Date: Tue, 16 Jan 2018 15:17:29 +0100 Message-Id: <1516112253-14480-48-git-send-email-pbonzini@redhat.com> In-Reply-To: <1516112253-14480-1-git-send-email-pbonzini@redhat.com> References: <1516112253-14480-1-git-send-email-pbonzini@redhat.com> Subject: [Qemu-devel] [PULL 47/51] find_ram_offset: Align ram_addr_t allocation on long boundaries List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: "Dr. David Alan Gilbert" From: "Dr. David Alan Gilbert" The dirty bitmaps are built from 'long's and there is fast-path code for synchronising the case where the RAMBlock is aligned to the start of a long boundary. Align the allocation to this boundary to cause the fast path to be used. Offsets before change: 11398@1515169675.018566:find_ram_offset size: 0x1e0000 @ 0x8000000 11398@1515169675.020064:find_ram_offset size: 0x20000 @ 0x81e0000 11398@1515169675.020244:find_ram_offset size: 0x20000 @ 0x8200000 11398@1515169675.024343:find_ram_offset size: 0x1000000 @ 0x8220000 11398@1515169675.025154:find_ram_offset size: 0x10000 @ 0x9220000 11398@1515169675.027682:find_ram_offset size: 0x40000 @ 0x9230000 11398@1515169675.032921:find_ram_offset size: 0x200000 @ 0x9270000 11398@1515169675.033307:find_ram_offset size: 0x1000 @ 0x9470000 11398@1515169675.033601:find_ram_offset size: 0x1000 @ 0x9471000 after change: 10923@1515169108.818245:find_ram_offset size: 0x1e0000 @ 0x8000000 10923@1515169108.819410:find_ram_offset size: 0x20000 @ 0x8200000 10923@1515169108.819587:find_ram_offset size: 0x20000 @ 0x8240000 10923@1515169108.823708:find_ram_offset size: 0x1000000 @ 0x8280000 10923@1515169108.824503:find_ram_offset size: 0x10000 @ 0x9280000 10923@1515169108.827093:find_ram_offset size: 0x40000 @ 0x92c0000 10923@1515169108.833045:find_ram_offset size: 0x200000 @ 0x9300000 10923@1515169108.833504:find_ram_offset size: 0x1000 @ 0x9500000 10923@1515169108.833787:find_ram_offset size: 0x1000 @ 0x9540000 Suggested-by: Paolo Bonzini Signed-off-by: Dr. David Alan Gilbert Message-Id: <20180105170138.23357-3-dgilbert@redhat.com> Signed-off-by: Paolo Bonzini --- exec.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/exec.c b/exec.c index 5e2fb55..9f4f450 100644 --- a/exec.c +++ b/exec.c @@ -1678,7 +1678,11 @@ static ram_addr_t find_ram_offset(ram_addr_t size) RAMBLOCK_FOREACH(block) { ram_addr_t candidate, next = RAM_ADDR_MAX; + /* Align blocks to start on a 'long' in the bitmap + * which makes the bitmap sync'ing take the fast path. + */ candidate = block->offset + block->max_length; + candidate = ROUND_UP(candidate, BITS_PER_LONG << TARGET_PAGE_BITS); /* Search for the closest following block * and find the gap. -- 1.8.3.1