From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by sourceware.org (Postfix) with ESMTPS id BC026388264A for ; Thu, 25 May 2023 08:11:38 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.2 sourceware.org BC026388264A Authentication-Results: sourceware.org; dmarc=pass (p=none dis=none) header.from=redhat.com Authentication-Results: sourceware.org; spf=pass smtp.mailfrom=redhat.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1685002298; 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=mC7ygBpoN2FsyEaYxdgXNQrWZoQeq2aZyLmzAReRRWg=; b=PUoBUrNOhnznLVycgtdCURLOc/7F0W71jDO3dObfMW46H9nBhPCnezmWWimham9vSAkl8Q PDieKQxEa/NGP/x8fuJGUIb/lw3X+FHNnbvFocc2TX8WE3o80bDmhYfZa0Q1csnHrsTUha fbNTtkQjC6dthuVVSMdNQ2mgLTapwj0= Received: from mimecast-mx02.redhat.com (mx3-rdu2.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-83-91pAdTm7PpW6Lu_3N_Q3BA-1; Thu, 25 May 2023 04:11:36 -0400 X-MC-Unique: 91pAdTm7PpW6Lu_3N_Q3BA-1 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.rdu2.redhat.com [10.11.54.8]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 69A6B28EC112; Thu, 25 May 2023 08:11:36 +0000 (UTC) Received: from oldenburg.str.redhat.com (unknown [10.2.16.8]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 61EC1C0448E; Thu, 25 May 2023 08:11:35 +0000 (UTC) From: Florian Weimer To: Noah Goldstein Cc: Noah Goldstein via Libc-alpha , hjl.tools@gmail.com, carlos@systemhalted.org Subject: Re: [PATCH v1] x86: Use 64MB as nt-store threshold if no cacheinfo [BZ #30429] References: <20230509031020.3496291-1-goldstein.w.n@gmail.com> <87wn1h6fya.fsf@oldenburg.str.redhat.com> Date: Thu, 25 May 2023 10:11:33 +0200 In-Reply-To: (Noah Goldstein's message of "Tue, 9 May 2023 11:01:42 -0500") Message-ID: <87lehcomoa.fsf@oldenburg.str.redhat.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/28.2 (gnu/linux) MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.1 on 10.11.54.8 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable X-Spam-Status: No, score=-4.9 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH,DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_NONE,RCVD_IN_MSPIKE_H2,SPF_HELO_NONE,SPF_NONE,TXREP,T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on server2.sourceware.org List-Id: * Noah Goldstein: > On Tue, May 9, 2023 at 3:56=E2=80=AFAM Florian Weimer wrote: >> >> * Noah Goldstein via Libc-alpha: >> >> > If `non_temporal_threshold` is below `minimum_non_temporal_threshold`, >> > it almost certainly means we failed to read the systems cache info. >> > >> > In this case, rather than defaulting the minimum correct value, we >> > should default to a value that gets at least reasonable >> > performance. 64MB is chosen conservatively to be at the very high >> > end. This should never cause non-temporal stores when, if we had read >> > cache info, we wouldn't have otherwise. >> >> I think that's quite surprising for GLIBC_TUNABLES. Maybe that logic >> should only activate if the default was set from cache sizes? >> > I don't quite understand what you mean by "only active if the default > was set from cache sizes"? > > This logic only triggers if total_cachesize / 8 < ~16kb. I think this sho= uld > only ever really happen if we failed to read cache info. What is the > surprise? Right, my mistake. The patch should work as-is. Reviewed-by: Florian Weimer Thanks, Florian