From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id E419BCFB440 for ; Mon, 7 Oct 2024 08:43:27 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1sxjKS-0007Rk-CN; Mon, 07 Oct 2024 04:42:56 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1sxjKQ-0007Ra-Eb for qemu-devel@nongnu.org; Mon, 07 Oct 2024 04:42:54 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1sxjKO-000703-Jb for qemu-devel@nongnu.org; Mon, 07 Oct 2024 04:42:54 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1728290571; h=from:from:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:in-reply-to:in-reply-to: references:references; bh=hgwzmtV5BraAQTKXC4qHZt7MlwzUlfHpJhq4r3pomqI=; b=JreRFqYL9E7TYbI9YSYCJ5BqkCbCQoIY9AwtFxKZDHq2dKQ+MAE5qYyghceA8MENd4hoIZ c7tukU8F9XNrMJNOH/MeIVwWMjz6zRVAAG3BRgDSVwEBZAw+Zm8ogMmW9aFbBvGHkT1zBy 3bmMA/cwMNlrP17julF7xg23QbLOfxg= Received: from mx-prod-mc-02.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-231-6pVX0G-8NNuKdY8Qin9wDw-1; Mon, 07 Oct 2024 04:42:48 -0400 X-MC-Unique: 6pVX0G-8NNuKdY8Qin9wDw-1 Received: from mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.12]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-02.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id F08F9195419F; Mon, 7 Oct 2024 08:42:46 +0000 (UTC) Received: from redhat.com (unknown [10.42.28.61]) by mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 1D6F619560AE; Mon, 7 Oct 2024 08:42:43 +0000 (UTC) Date: Mon, 7 Oct 2024 09:42:40 +0100 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Pierrick Bouvier Cc: qemu-devel@nongnu.org, alex.bennee@linaro.org, Paolo Bonzini , richard.henderson@linaro.org, =?utf-8?Q?Marc-Andr=C3=A9?= Lureau , Philippe =?utf-8?Q?Mathieu-Daud=C3=A9?= Subject: Re: [PATCH] meson: ensure we enable CMPXCHG128 on x86_64 Message-ID: References: <20241004220123.978938-1-pierrick.bouvier@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20241004220123.978938-1-pierrick.bouvier@linaro.org> User-Agent: Mutt/2.2.12 (2023-09-09) X-Scanned-By: MIMEDefang 3.0 on 10.30.177.12 Received-SPF: pass client-ip=170.10.129.124; envelope-from=berrange@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -22 X-Spam_score: -2.3 X-Spam_bar: -- X-Spam_report: (-2.3 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.151, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H3=-0.01, RCVD_IN_MSPIKE_WL=-0.01, RCVD_IN_VALIDITY_CERTIFIED_BLOCKED=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On Fri, Oct 04, 2024 at 03:01:23PM -0700, Pierrick Bouvier wrote: > Alex discovered that CMPXCHG128 was not enabled when building for > x86_64, resulting in slow execution for wide atomic instructions, > creating a huge contention when combined with a high number of cpus > (found while booting android aarch64 guest on x86_64 host). > > The problem is that even though we enable -mcx16 option for x86_64, this > is not used when testing for CMPXCHG128. Thus, we silently turn it off. > > x86_64 is the only architecture adding machine flags for now, so the > problem is limited to this host architecture. > > Meson compiler tests are supposed to be independent of environment flags > (https://mesonbuild.com/Reference-manual_returned_compiler.html#returned-by). > However, CFLAGS are used anyway, thus masking the problem when using > something like CFLAGS='-march=native'. This is a meson bug and was reported: > https://github.com/mesonbuild/meson/issues/13757 > > Signed-off-by: Pierrick Bouvier > --- > meson.build | 10 +++++++++- > 1 file changed, 9 insertions(+), 1 deletion(-) > > diff --git a/meson.build b/meson.build > index b18c2a54ab5..af2ce595dcc 100644 > --- a/meson.build > +++ b/meson.build > @@ -2867,6 +2867,13 @@ if has_int128_type > config_host_data.set('CONFIG_ATOMIC128_OPT', has_atomic128_opt) > > if not has_atomic128_opt > + > + host_flags = [] > + if host_arch == 'x86_64' > + # for x86_64, x86_version must be >= 1, and we always enable cmpxchg16 > + # in this case. > + host_flags += ['-mcx16'] > + endif IMHO, we shouldn't be assuming that the earlier code passed '-mcx16', as it requires that we keep 2 far away parts of meson.build in sync. > config_host_data.set('CONFIG_CMPXCHG128', cc.links(''' > int main(void) > { > @@ -2874,7 +2881,8 @@ if has_int128_type > __sync_val_compare_and_swap_16(&x, y, x); > return 0; > } > - ''')) > + ''', > + args: host_flags)) Just pass 'qemu_common_flags' here. > endif > endif > endif With regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|