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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7141AC4332F for ; Wed, 2 Nov 2022 12:01:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231132AbiKBMBV convert rfc822-to-8bit (ORCPT ); Wed, 2 Nov 2022 08:01:21 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60198 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231171AbiKBMBB (ORCPT ); Wed, 2 Nov 2022 08:01:01 -0400 Received: from eu-smtp-delivery-151.mimecast.com (eu-smtp-delivery-151.mimecast.com [185.58.85.151]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0723929373 for ; Wed, 2 Nov 2022 05:00:56 -0700 (PDT) Received: from AcuMS.aculab.com (156.67.243.121 [156.67.243.121]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384) id uk-mta-258-1yQNw3MuPJOLWPGjyRulkQ-1; Wed, 02 Nov 2022 12:00:53 +0000 X-MC-Unique: 1yQNw3MuPJOLWPGjyRulkQ-1 Received: from AcuMS.Aculab.com (10.202.163.4) by AcuMS.aculab.com (10.202.163.4) with Microsoft SMTP Server (TLS) id 15.0.1497.42; Wed, 2 Nov 2022 12:00:51 +0000 Received: from AcuMS.Aculab.com ([::1]) by AcuMS.aculab.com ([::1]) with mapi id 15.00.1497.042; Wed, 2 Nov 2022 12:00:51 +0000 From: David Laight To: 'Zhen Lei' , Josh Poimboeuf , Jiri Kosina , Miroslav Benes , Petr Mladek , Joe Lawrence , "live-patching@vger.kernel.org" , "linux-kernel@vger.kernel.org" , Masahiro Yamada , Alexei Starovoitov , Jiri Olsa , Kees Cook , Andrew Morton , "Luis Chamberlain" , "linux-modules@vger.kernel.org" , Steven Rostedt , "Ingo Molnar" Subject: RE: [PATCH v8 4/9] kallsyms: Reduce the memory occupied by kallsyms_seqs_of_names[] Thread-Topic: [PATCH v8 4/9] kallsyms: Reduce the memory occupied by kallsyms_seqs_of_names[] Thread-Index: AQHY7pgsdRO9dUiW6k27i3NhSmpxX64riAdg Date: Wed, 2 Nov 2022 12:00:51 +0000 Message-ID: References: <20221102084921.1615-1-thunder.leizhen@huawei.com> <20221102084921.1615-5-thunder.leizhen@huawei.com> In-Reply-To: <20221102084921.1615-5-thunder.leizhen@huawei.com> Accept-Language: en-GB, en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-ms-exchange-transport-fromentityheader: Hosted x-originating-ip: [10.202.205.107] MIME-Version: 1.0 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: aculab.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Zhen Lei > Sent: 02 November 2022 08:49 > > kallsyms_seqs_of_names[] records the symbol index sorted by address, the > maximum value in kallsyms_seqs_of_names[] is the number of symbols. And > 2^24 = 16777216, which means that three bytes are enough to store the > index. This can help us save (1 * kallsyms_num_syms) bytes of memory. You can get the compiler to do the 'heavy lifting' for you. struct uint24 { unsigned int val24:24; } __attribute__((packed)); struct uint24 table[1024]; works fine. David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)