From patchwork Mon Jul 18 09:27:49 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Paolo Bonzini X-Patchwork-Id: 72190 Delivered-To: patch@linaro.org Received: by 10.140.29.52 with SMTP id a49csp14791qga; Mon, 18 Jul 2016 02:45:21 -0700 (PDT) X-Received: by 10.55.180.2 with SMTP id d2mr42161102qkf.69.1468835121234; Mon, 18 Jul 2016 02:45:21 -0700 (PDT) Return-Path: Received: from lists.gnu.org (lists.gnu.org. [2001:4830:134:3::11]) by mx.google.com with ESMTPS id 1si5411286qkh.164.2016.07.18.02.45.21 for (version=TLS1 cipher=AES128-SHA bits=128/128); Mon, 18 Jul 2016 02:45:21 -0700 (PDT) Received-SPF: pass (google.com: domain of qemu-devel-bounces+patch=linaro.org@nongnu.org designates 2001:4830:134:3::11 as permitted sender) client-ip=2001:4830:134:3::11; Authentication-Results: mx.google.com; spf=pass (google.com: domain of qemu-devel-bounces+patch=linaro.org@nongnu.org designates 2001:4830:134:3::11 as permitted sender) smtp.mailfrom=qemu-devel-bounces+patch=linaro.org@nongnu.org Received: from localhost ([::1]:45461 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bP572-0007B5-Ok for patch@linaro.org; Mon, 18 Jul 2016 05:45:20 -0400 Received: from eggs.gnu.org ([2001:4830:134:3::10]:36377) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bP4qn-0004j4-5K for qemu-devel@nongnu.org; Mon, 18 Jul 2016 05:28:37 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1bP4qm-0006dD-1M for qemu-devel@nongnu.org; Mon, 18 Jul 2016 05:28:33 -0400 Received: from mx1.redhat.com ([209.132.183.28]:33961) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bP4ql-0006d8-Oq for qemu-devel@nongnu.org; Mon, 18 Jul 2016 05:28:31 -0400 Received: from int-mx14.intmail.prod.int.phx2.redhat.com (int-mx14.intmail.prod.int.phx2.redhat.com [10.5.11.27]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id AA9E644800; Mon, 18 Jul 2016 09:28:30 +0000 (UTC) Received: from donizetti.redhat.com (ovpn-112-56.ams2.redhat.com [10.36.112.56]) by int-mx14.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id u6I9RuJC025611; Mon, 18 Jul 2016 05:28:28 -0400 From: Paolo Bonzini To: qemu-devel@nongnu.org Date: Mon, 18 Jul 2016 11:27:49 +0200 Message-Id: <1468834075-25669-18-git-send-email-pbonzini@redhat.com> In-Reply-To: <1468834075-25669-1-git-send-email-pbonzini@redhat.com> References: <1468834075-25669-1-git-send-email-pbonzini@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.68 on 10.5.11.27 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.30]); Mon, 18 Jul 2016 09:28:30 +0000 (UTC) X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 209.132.183.28 Subject: [Qemu-devel] [PULL 17/23] tcg: 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: =?UTF-8?q?Alex=20Benn=C3=A9e?= , Sergey Fedorov Errors-To: qemu-devel-bounces+patch=linaro.org@nongnu.org Sender: "Qemu-devel" From: Alex Bennée 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 Reviewed-by: Sergey Fedorov Signed-off-by: Sergey Fedorov Message-Id: <20160715175852.30749-10-sergey.fedorov@linaro.org> Signed-off-by: Paolo Bonzini --- cpu-exec.c | 48 +++++++++++++++++++++--------------------------- 1 file changed, 21 insertions(+), 27 deletions(-) -- 2.7.4 diff --git a/cpu-exec.c b/cpu-exec.c index 6c40839..97e18f7 100644 --- a/cpu-exec.c +++ b/cpu-exec.c @@ -286,35 +286,29 @@ static TranslationBlock *tb_find_slow(CPUState *cpu, TranslationBlock *tb; 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; } @@ -332,7 +326,6 @@ 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 || atomic_read(&tb->pc) != pc || atomic_read(&tb->cs_base) != cs_base || @@ -350,14 +343,15 @@ static inline TranslationBlock *tb_find_fast(CPUState *cpu, #endif /* See if we can patch the calling TB. */ if (last_tb && !qemu_loglevel_mask(CPU_LOG_TB_NOCHAIN)) { + tb_lock(); /* Check if translation buffer has been flushed */ if (cpu->tb_flushed) { cpu->tb_flushed = false; } else if (!tb_is_invalid(tb)) { tb_add_jump(last_tb, tb_exit, tb); } + tb_unlock(); } - tb_unlock(); return tb; }