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 ACF46C00140 for ; Fri, 29 Jul 2022 02:01:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233806AbiG2CBZ (ORCPT ); Thu, 28 Jul 2022 22:01:25 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55806 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232420AbiG2CBY (ORCPT ); Thu, 28 Jul 2022 22:01:24 -0400 Received: from mail-wr1-x434.google.com (mail-wr1-x434.google.com [IPv6:2a00:1450:4864:20::434]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 4B92A78DFA for ; Thu, 28 Jul 2022 19:01:23 -0700 (PDT) Received: by mail-wr1-x434.google.com with SMTP id p10so118957wru.8 for ; Thu, 28 Jul 2022 19:01:23 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=fKo8b4je0iqGq0uiZqH7zNlb83Vh1FNB/a+r4AK80T8=; b=qh/wY2GLSdmFq98iuNUcPy+KISCMDt6bBos/1GYLClu9zYRT/nXaP5i+OJ8hXmfVO6 UXskbmrAJp4z/3BdcnKPVmml7oVvCQ7bXKvfMOYp9kt2psTEm3gGWndKuoWJzn4nq/Xr RO77QEI12dSndxUphWJJYr6AR2gmPIa4wKvB286Z92abF3FDI/bREF0n1EK7gZ20GbXk j+C1LiRus03zDSAWa5zspECdBRh0egOKxK4KH0/Y9Jsl5mnGCa8EOl1u2pYUJf3Tcwtt zzhJVyewPd6rv6b9xZvVXMMAGskp7iBeqCnx2dmhiyMaX/9z7WZyyfn9xEDHdsKfyzVu mURw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=fKo8b4je0iqGq0uiZqH7zNlb83Vh1FNB/a+r4AK80T8=; b=lHERMzHJFgwYblRxcO7YaTmx+9ciPr7rYkI6Qt5SfUm0A6tIWESTzgWx00TtdL4OjA sPCjk5Pvx4NcoqbbP6TPbgdmBoTsFXiazHGXKjwR5e28fnLTunxUTaTDPK68lbXu2XRP J3rmA88gEfcqL31kZ7JFj8aWfO8lEPcDmIx/Cb/TQl37ontpP76C41bv4wkuc2DbVnzD AnZTeoAB46WecZLy6TIbzz+07NpfCHBOmkJHCz3VJIb+tBDxHsQfwFQmceyzEDlLrK/Q HgEpnLfRGZpojLPKQIBphzVTe1iBATeoBP9qOkzQnMxuTWhRgV8po4x3815LHPXfgCuJ uRvw== X-Gm-Message-State: ACgBeo3f2r6yk55xnAnkIT3YjqE4Xz7v2KcpqqWtkdg+G6hOq4vngna7 G3ULuIgO3pXg0cQfr5GtKJHv5z2VhAC6XaaHTSk6Ng== X-Google-Smtp-Source: AA6agR5cPNsIfML6yyQKPbDjRDBRwyuxiIL3O1NzD4HMAqamz2pbk6MDyllQ67IBlyD/TQOOtay5gTHQrQvjOVSig1Y= X-Received: by 2002:a5d:6d4e:0:b0:21e:660e:55bf with SMTP id k14-20020a5d6d4e000000b0021e660e55bfmr824800wri.343.1659060081456; Thu, 28 Jul 2022 19:01:21 -0700 (PDT) MIME-Version: 1.0 References: <20220614143353.1559597-1-irogers@google.com> In-Reply-To: From: Ian Rogers Date: Thu, 28 Jul 2022 19:01:09 -0700 Message-ID: Subject: Re: [PATCH v2 0/6] Corrections to cpu map event encoding To: Peter Zijlstra , Ingo Molnar , Arnaldo Carvalho de Melo , Mark Rutland , Alexander Shishkin , Jiri Olsa , Namhyung Kim , James Clark , Kees Cook , "Gustavo A. R. Silva" , Adrian Hunter , Riccardo Mancini , German Gomez , Colin Ian King , Song Liu , Dave Marchevsky , Athira Rajeev , Alexey Bayduraev , Leo Yan , linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org Cc: Stephane Eranian Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-perf-users@vger.kernel.org On Fri, Jul 15, 2022 at 10:01 AM Ian Rogers wrote: > > On Tue, Jun 14, 2022 at 7:33 AM Ian Rogers wrote: > > > > A mask encoding of a cpu map is laid out as: > > u16 nr > > u16 long_size > > unsigned long mask[]; > > However, the mask may be 8-byte aligned meaning there is a 4-byte pad > > after long_size. This means 32-bit and 64-bit builds see the mask as > > being at different offsets. On top of this the structure is in the byte > > data[] encoded as: > > u16 type > > char data[] > > This means the mask's struct isn't the required 4 or 8 byte aligned, but > > is offset by 2. Consequently the long reads and writes are causing > > undefined behavior as the alignment is broken. > > > > These changes do minor clean up with const, visibility of functions > > and using the constant time max function. It then adds 32 and 64-bit > > mask encoding variants, packed to match current alignment. Taking the > > address of a packed struct leads to unaligned data, so function > > arguments are altered to be passed the packed struct. To compact the > > mask encoding further and drop the padding, the 4-byte variant is > > preferred. Finally a new range encoding is added, that reduces the > > size of the common case of a range of CPUs to a single u64. > > > > On a 72 CPU (hyperthread) machine the original encoding of all CPUs is: > > 0x9a98 [0x28]: event: 74 > > . > > . ... raw event: size 40 bytes > > . 0000: 4a 00 00 00 00 00 28 00 01 00 02 00 08 00 00 00 J.....(......... > > . 0010: 00 00 ff ff ff ff ff ff ff ff ff 00 00 00 00 00 ................ > > . 0020: 00 00 00 00 00 00 00 00 ........ > > > > 0 0 0x9a98 [0x28]: PERF_RECORD_CPU_MAP > > > > Using the 4-byte encoding it is: > > 0x9a98@pipe [0x20]: event: 74 > > . > > . ... raw event: size 32 bytes > > . 0000: 4a 00 00 00 00 00 20 00 01 00 03 00 04 00 ff ff J..... ......... > > . 0010: ff ff ff ff ff ff ff 00 00 00 00 00 00 00 00 00 ................ > > > > 0 0 0x9a98 [0x20]: PERF_RECORD_CPU_MAP > > > > Finally, with the range encoding it is: > > 0x9ab8@pipe [0x10]: event: 74 > > . > > . ... raw event: size 16 bytes > > . 0000: 4a 00 00 00 00 00 10 00 02 00 00 00 00 00 47 00 J.............G. > > > > 0 0 0x9ab8 [0x10]: PERF_RECORD_CPU_MAP > > > > v2. Fixes a bug in the size computation of the update header > > introduced by the last patch (Add range data encoding) and caught > > by address sanitizer. > > > > Ian Rogers (6): > > perf cpumap: Const map for max > > perf cpumap: Synthetic events and const/static > > perf cpumap: Compute mask size in constant time > > perf cpumap: Fix alignment for masks in event encoding > > perf events: Prefer union over variable length array > > perf cpumap: Add range data encoding > > Ping. There was some feedback on this change but nothing to create a > v3. Feedback/acked-by/reviewed-by appreciated. Ping. Feedback appreciated. Thanks, Ian > Thanks, > Ian > > > tools/lib/perf/cpumap.c | 2 +- > > tools/lib/perf/include/perf/cpumap.h | 2 +- > > tools/lib/perf/include/perf/event.h | 61 ++++++++- > > tools/perf/tests/cpumap.c | 71 ++++++++--- > > tools/perf/tests/event_update.c | 14 +-- > > tools/perf/util/cpumap.c | 111 +++++++++++++--- > > tools/perf/util/cpumap.h | 4 +- > > tools/perf/util/event.h | 4 - > > tools/perf/util/header.c | 24 ++-- > > tools/perf/util/session.c | 35 +++--- > > tools/perf/util/synthetic-events.c | 182 +++++++++++++-------------- > > tools/perf/util/synthetic-events.h | 2 +- > > 12 files changed, 327 insertions(+), 185 deletions(-) > > > > -- > > 2.36.1.476.g0c4daa206d-goog > >