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 [63.128.21.124]) by sourceware.org (Postfix) with ESMTP id 122753857C62 for ; Mon, 5 Oct 2020 09:47:51 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.3.2 sourceware.org 122753857C62 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-548-Ad-o0snyNUO4Q51XidBX-w-1; Mon, 05 Oct 2020 05:47:36 -0400 X-MC-Unique: Ad-o0snyNUO4Q51XidBX-w-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 4358E80EDA8; Mon, 5 Oct 2020 09:47:35 +0000 (UTC) Received: from oldenburg2.str.redhat.com (ovpn-113-11.ams2.redhat.com [10.36.113.11]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 88C545D9CA; Mon, 5 Oct 2020 09:47:34 +0000 (UTC) From: Florian Weimer To: "Paul A. Clarke" Cc: libc-alpha@sourceware.org Subject: Re: [PATCH 18/28] powerpc64le: Add glibc-hwcaps support References: <01faff4932d02c7e3224b50a1cdb5956354b1fc2.1601569371.git.fweimer@redhat.com> <20201001185639.GA132840@li-24c3614c-2adc-11b2-a85c-85f334518bdb.ibm.com> Date: Mon, 05 Oct 2020 11:47:32 +0200 In-Reply-To: <20201001185639.GA132840@li-24c3614c-2adc-11b2-a85c-85f334518bdb.ibm.com> (Paul A. Clarke's message of "Thu, 1 Oct 2020 13:56:39 -0500") Message-ID: <87ft6txavf.fsf@oldenburg2.str.redhat.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.1 (gnu/linux) MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain X-Spam-Status: No, score=-11.8 required=5.0 tests=BAYES_00, DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, GIT_PATCH_0, KAM_SHORT, RCVD_IN_DNSWL_NONE, RCVD_IN_MSPIKE_H5, RCVD_IN_MSPIKE_WL, SPF_HELO_NONE, SPF_PASS, TXREP autolearn=ham autolearn_force=no version=3.4.2 X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on server2.sourceware.org X-BeenThere: libc-alpha@sourceware.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Libc-alpha mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 05 Oct 2020 09:47:52 -0000 * Paul A. Clarke: >> diff --git a/sysdeps/powerpc/powerpc64/le/dl-hwcaps-subdirs.c b/sysdeps/powerpc/powerpc64/le/dl-hwcaps-subdirs.c >> new file mode 100644 >> index 0000000000..496daf0fa0 >> --- /dev/null >> +++ b/sysdeps/powerpc/powerpc64/le/dl-hwcaps-subdirs.c >> @@ -0,0 +1,34 @@ >> +/* Architecture-specific glibc-hwcaps subdirectories. powerpc64le version. >> + Copyright (C) 2020 Free Software Foundation, Inc. >> + This file is part of the GNU C Library. >> + >> + The GNU C Library is free software; you can redistribute it and/or >> + modify it under the terms of the GNU Lesser General Public >> + License as published by the Free Software Foundation; either >> + version 2.1 of the License, or (at your option) any later version. >> + >> + The GNU C Library is distributed in the hope that it will be useful, >> + but WITHOUT ANY WARRANTY; without even the implied warranty of >> + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU >> + Lesser General Public License for more details. >> + >> + You should have received a copy of the GNU Lesser General Public >> + License along with the GNU C Library; if not, see >> + . */ >> + >> +#include >> +#include >> + >> +const char _dl_hwcaps_subdirs[] = "power10:power9"; >> + >> +int32_t > > Is 32 bits enough? Any reason not to make this 64 bits? It's enough for now for all the targets that have glibc-hwcaps support so far. It's a strictly internal interface, so it's easy to change later. We also need to consider the impact on library path processing. Even just 20 additional open & stat calls for each LD_LIBRARY_PATH entry might be quite visible in process startup benchmarks. So I'm not sure if we will ever use those 32 bits. >> +_dl_hwcaps_subdirs_active (void) >> +{ >> + if (GLRO (dl_hwcap2) & PPC_FEATURE2_ARCH_3_1) >> + return 3; >> + >> + if (GLRO (dl_hwcap2) & PPC_FEATURE2_ARCH_3_00) >> + return 1; > > Is there some way to tie these magic numbers closer to their meaning? Would you please have a look at the the x86-64 implementation and check if it is closer to your liking? > Perhaps something like (not tested): > -- > const char * const _dl_hwcaps_subdirs[] = { > #define _DL_HWCAPS_SUBDIR_POWER10_BIT 0x2 /* or 1 to preserve same order. */ > "power10", > #define _DL_HWCAPS_SUBDIR_POWER9_BIT 0x1 /* or 2. */ > "power9" > }; > > int32_t > _dl_hwcaps_subdirs_active (void) > { > int32_t result = 0; > > if (GLRO (dl_hwcap2) & PPC_FEATURE2_ARCH_3_1) > result |= _DL_HWCAPS_SUBDIR_POWER10_BIT; > > if (GLRO (dl_hwcap2) & PPC_FEATURE2_ARCH_3_00) > result |= _DL_HWCAPS_SUBDIR_POWER9_BIT; > > return result; > } > -- > > Of course, that would require changes to the code that parses > _dl_hwcaps_subdirs. I chose the current approach to avoid relocations and memory allocations for processing hwcaps settings (e.g. from the ld.so command line). Thanks, Florian -- Red Hat GmbH, https://de.redhat.com/ , Registered seat: Grasbrunn, Commercial register: Amtsgericht Muenchen, HRB 153243, Managing Directors: Charles Cachera, Brian Klemm, Laurie Krebs, Michael O'Neill