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[209.51.188.17]) by mx.google.com with ESMTPS id m18si720341qka.225.2020.02.26.02.15.25 for (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Wed, 26 Feb 2020 02:15:25 -0800 (PST) Received-SPF: pass (google.com: domain of qemu-devel-bounces+alex.bennee=linaro.org@nongnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; Authentication-Results: mx.google.com; dkim=fail header.i=@redhat.com header.s=mimecast20190719 header.b=gp0+l4XQ; spf=pass (google.com: domain of qemu-devel-bounces+alex.bennee=linaro.org@nongnu.org designates 209.51.188.17 as permitted sender) smtp.mailfrom="qemu-devel-bounces+alex.bennee=linaro.org@nongnu.org"; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=redhat.com Received: from localhost ([::1]:41816 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1j6tiv-0006Vx-0K for alex.bennee@linaro.org; Wed, 26 Feb 2020 05:15:25 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:45819) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1j6tiS-0006TW-Lz for qemu-devel@nongnu.org; Wed, 26 Feb 2020 05:14:57 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1j6tiR-0000WO-JG for qemu-devel@nongnu.org; Wed, 26 Feb 2020 05:14:56 -0500 Received: from us-smtp-delivery-1.mimecast.com ([207.211.31.120]:20347 helo=us-smtp-1.mimecast.com) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1j6tiR-0000UW-EB for qemu-devel@nongnu.org; Wed, 26 Feb 2020 05:14:55 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1582712095; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=om53qjwnSjS90lVeCMzUxfnCbW/2PR9vmbVCQeD5U9w=; b=gp0+l4XQNXoDEOJjz0C/HAwDhfyPuXKHZjT4hSFyQm491X3otRetvD1mymHgBiecGqGiQy Yd3DIxk6UYyxr5IpHeE+Z6tzhp7Ev62CThH5ZRbAA3WdUC4xw3cqB2fJp8RqoEtP4lD8Pw 54CkmRqTKXjsAqVSAIBr/rqQ3bBXL0I= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-395-royBeu5qPTWcSnczuQIqMg-1; Wed, 26 Feb 2020 05:14:53 -0500 X-MC-Unique: royBeu5qPTWcSnczuQIqMg-1 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 49A7A1005512; Wed, 26 Feb 2020 10:14:52 +0000 (UTC) Received: from localhost (unknown [10.43.2.114]) by smtp.corp.redhat.com (Postfix) with ESMTP id C78B819C58; Wed, 26 Feb 2020 10:14:50 +0000 (UTC) Date: Wed, 26 Feb 2020 11:14:49 +0100 From: Igor Mammedov To: Howard Spoelstra Subject: Re: Sudden slowdown of ARM emulation in master Message-ID: <20200226111449.27530c6b@redhat.com> In-Reply-To: References: <20200226101948.786be4b0@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 207.211.31.120 X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Peter Maydell , QEMU Developers , Niek Linnenbank , qemu-arm , Paolo Bonzini , Philippe =?UTF-8?B?TWF0aGlldS1EYXVkw6k=?= Errors-To: qemu-devel-bounces+alex.bennee=linaro.org@nongnu.org Sender: "Qemu-devel" X-TUID: w1ZwbsYVE2x1 On Wed, 26 Feb 2020 10:32:38 +0100 Howard Spoelstra wrote: > On Wed, Feb 26, 2020 at 10:19 AM Igor Mammedov wrote: > > > On Wed, 26 Feb 2020 00:07:55 +0100 > > Niek Linnenbank wrote: > > > > > Hello Igor and Paolo, > > > > does following hack solves issue? > > > > diff --git a/accel/tcg/translate-all.c b/accel/tcg/translate-all.c > > index a08ab11f65..ab2448c5aa 100644 > > --- a/accel/tcg/translate-all.c > > +++ b/accel/tcg/translate-all.c > > @@ -944,7 +944,7 @@ static inline size_t size_code_gen_buffer(size_t > > tb_size) > > /* ??? If we relax the requirement that CONFIG_USER_ONLY use the > > static buffer, we could size this on RESERVED_VA, on the text > > segment size of the executable, or continue to use the > > default. */ > > - tb_size = (unsigned long)(ram_size / 4); > > + tb_size = MAX_CODE_GEN_BUFFER_SIZE; > > #endif > > } > > if (tb_size < MIN_CODE_GEN_BUFFER_SIZE) { > > > > > > Nice, for me, that brings qemu-system-ppc back up to speed. (applied to > ppc-for-5.0) thanks for confirming. My patch a1b18df9a4 'vl.c: move -m parsing after memory backends has been processed' moved ram_size parsing after accelerator init, but tcg allocates buffer based on global ram_size and since ram_size is still 0 it falls back to MIN_CODE_GEN_BUFFER_SIZE (see size_code_gen_buffer) and if ram_size were too large it would cap buffet at MAX_CODE_GEN_BUFFER_SIZE. *-user doesn't use ram_size, it uses DEFAULT_CODE_GEN_BUFFER_SIZE and static buffer so it's no affected. For softmmu it should be possible to postpone buffer allocation till accel_setup_post(current_machine) time and fetch ram_size from current machine dropping random access to global variable. That would put buffer allocation after ram_size is parsed. Does it look like a feasible approach? > > Best, > Howard