From patchwork Fri Jul 1 16:16:10 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: =?utf-8?q?Alex_Benn=C3=A9e?= X-Patchwork-Id: 643118 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Received: from lists.gnu.org (lists.gnu.org [IPv6:2001:4830:134:3::11]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (No client certificate requested) by ozlabs.org (Postfix) with ESMTPS id 3rh20D0bJBz9s9x for ; Sat, 2 Jul 2016 02:28:28 +1000 (AEST) Authentication-Results: ozlabs.org; dkim=fail reason="signature verification failed" (1024-bit key; unprotected) header.d=linaro.org header.i=@linaro.org header.b=O6aMNWDI; dkim-atps=neutral Received: from localhost ([::1]:34448 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bJ1In-00067W-Qf for incoming@patchwork.ozlabs.org; Fri, 01 Jul 2016 12:28:25 -0400 Received: from eggs.gnu.org ([2001:4830:134:3::10]:42784) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bJ171-000885-4m for qemu-devel@nongnu.org; Fri, 01 Jul 2016 12:16:16 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1bJ16v-0002ab-Qd for qemu-devel@nongnu.org; Fri, 01 Jul 2016 12:16:14 -0400 Received: from mail-wm0-x22e.google.com ([2a00:1450:400c:c09::22e]:34667) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bJ16v-0002aP-GI for qemu-devel@nongnu.org; Fri, 01 Jul 2016 12:16:09 -0400 Received: by mail-wm0-x22e.google.com with SMTP id 187so10972317wmz.1 for ; Fri, 01 Jul 2016 09:16:09 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=ai+lmtzIhpzkdeSxvlk0vxlL+ur74qkiyU0YUepZ3Ic=; b=O6aMNWDIZxh7D9hMe7tY0W8pZZziB4v4LuG658p+zziXtSGWnPCJZT3J9rgKvB6wa9 H3DOwwI1b+oX9xDTUKOK3hN8icKDe/dkJwaCKsZBgmjJ8tIG7GqaMFWsaOpcOwnniYF7 xSIdv2583IMw+jD2u27F/6ZOzQY7cTY1aErso= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=ai+lmtzIhpzkdeSxvlk0vxlL+ur74qkiyU0YUepZ3Ic=; b=kUcP63Hn1OAK47vIWbhJTVRCpBFn2glWrhQpkGzlOd4B0PQ4Oj9pECACNbPnmu8RJ/ jb0s1vQpP6DxGZLY68sCYsuuriz8Z4Dn8PiYoUMdDjoH7xfYt1NMAsL/lYrkZ4j2Dl2l 8Wmt9tpMaYH2NijO2iCn06s4pEaTtW9qC+ms7RXeUeWVrbEWR5JeD1vWUQx9Q+h38V80 E2mVhBmR3NubzCt4SHIr605RustbwzzQntjOAmkEsbh3kfNfiTXo/r503Y3pI2ouqPZf wtGiHvT6TrlE2rHxUaa33sDkWFn0pNBkq90FDwjnajpJTzxqkGA295Fx8XxiLseYdmIG +xDg== X-Gm-Message-State: ALyK8tInmHpdgMk21OKVr/E5yCn8bjmOFB/X68Xs+UGQ8E6UWtYRzUUoZgVD/dZBhDt12CVy X-Received: by 10.28.140.202 with SMTP id o193mr344427wmd.55.1467389768854; Fri, 01 Jul 2016 09:16:08 -0700 (PDT) Received: from zen.linaro.local ([81.128.185.34]) by smtp.gmail.com with ESMTPSA id w15sm5821881wmd.11.2016.07.01.09.16.05 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 01 Jul 2016 09:16:05 -0700 (PDT) Received: from zen.linaroharston (localhost [127.0.0.1]) by zen.linaro.local (Postfix) with ESMTP id 05BDC3E0524; Fri, 1 Jul 2016 17:16:12 +0100 (BST) From: =?UTF-8?q?Alex=20Benn=C3=A9e?= To: mttcg@listserver.greensocs.com, qemu-devel@nongnu.org, fred.konrad@greensocs.com, a.rigo@virtualopensystems.com, serge.fdrv@gmail.com, cota@braap.org, bobby.prani@gmail.com, rth@twiddle.net Date: Fri, 1 Jul 2016 17:16:10 +0100 Message-Id: <1467389770-9738-3-git-send-email-alex.bennee@linaro.org> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1467389770-9738-1-git-send-email-alex.bennee@linaro.org> References: <1467389770-9738-1-git-send-email-alex.bennee@linaro.org> MIME-Version: 1.0 X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 2a00:1450:400c:c09::22e Subject: [Qemu-devel] [PATCH 2/2] cpu-exec: remove tb_lock from the hot-path X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: peter.maydell@linaro.org, Peter Crosthwaite , claudio.fontana@huawei.com, mark.burton@greensocs.com, jan.kiszka@siemens.com, pbonzini@redhat.com, =?UTF-8?q?Alex=20Benn=C3=A9e?= Errors-To: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Sender: "Qemu-devel" Lock contention in the hot path of moving between existing patched TranslationBlocks is the main drag in multithreaded performance. This patch pushes the tb_lock() usage down to the two places that really need it: - code generation (tb_gen_code) - jump patching (tb_add_jump) The rest of the code doesn't really need to hold a lock as it is either using per-CPU structures, atomically updated or designed to be used in concurrent read situations (qht_lookup). To keep things simple I removed the #ifdef CONFIG_USER_ONLY stuff as the locks become NOPs anyway until the MTTCG work is completed. Signed-off-by: Alex Bennée Reviewed-by: Richard Henderson --- v3 - fix merge conflicts with Sergey's patch v4 - revert name tweaking - drop test jmp_list_next outside lock - mention lock NOPs in comments --- cpu-exec.c | 49 ++++++++++++++++++++++--------------------------- 1 file changed, 22 insertions(+), 27 deletions(-) diff --git a/cpu-exec.c b/cpu-exec.c index 10ce1cb..b731774 100644 --- a/cpu-exec.c +++ b/cpu-exec.c @@ -291,35 +291,29 @@ static TranslationBlock *tb_find_slow(CPUState *cpu, * Pairs with smp_wmb() in tb_phys_invalidate(). */ smp_rmb(); tb = tb_find_physical(cpu, pc, cs_base, flags); - if (tb) { - goto found; - } + if (!tb) { -#ifdef CONFIG_USER_ONLY - /* mmap_lock is needed by tb_gen_code, and mmap_lock must be - * taken outside tb_lock. Since we're momentarily dropping - * tb_lock, there's a chance that our desired tb has been - * translated. - */ - tb_unlock(); - mmap_lock(); - tb_lock(); - tb = tb_find_physical(cpu, pc, cs_base, flags); - if (tb) { - mmap_unlock(); - goto found; - } -#endif + /* mmap_lock is needed by tb_gen_code, and mmap_lock must be + * taken outside tb_lock. As system emulation is currently + * single threaded the locks are NOPs. + */ + mmap_lock(); + tb_lock(); - /* if no translated code available, then translate it now */ - tb = tb_gen_code(cpu, pc, cs_base, flags, 0); + /* There's a chance that our desired tb has been translated while + * taking the locks so we check again inside the lock. + */ + tb = tb_find_physical(cpu, pc, cs_base, flags); + if (!tb) { + /* if no translated code available, then translate it now */ + tb = tb_gen_code(cpu, pc, cs_base, flags, 0); + } -#ifdef CONFIG_USER_ONLY - mmap_unlock(); -#endif + tb_unlock(); + mmap_unlock(); + } -found: - /* we add the TB in the virtual pc hash table */ + /* We add the TB in the virtual pc hash table for the fast lookup */ atomic_set(&cpu->tb_jmp_cache[tb_jmp_cache_hash_func(pc)], tb); return tb; } @@ -337,7 +331,6 @@ static inline TranslationBlock *tb_find_fast(CPUState *cpu, always be the same before a given translated block is executed. */ cpu_get_tb_cpu_state(env, &pc, &cs_base, &flags); - tb_lock(); tb = atomic_read(&cpu->tb_jmp_cache[tb_jmp_cache_hash_func(pc)]); if (unlikely(!tb || tb->pc != pc || tb->cs_base != cs_base || tb->flags != flags)) { @@ -359,11 +352,13 @@ static inline TranslationBlock *tb_find_fast(CPUState *cpu, *last_tb = NULL; } #endif + /* See if we can patch the calling TB. */ if (*last_tb && !qemu_loglevel_mask(CPU_LOG_TB_NOCHAIN)) { + tb_lock(); tb_add_jump(*last_tb, tb_exit, tb); + tb_unlock(); } - tb_unlock(); return tb; }