From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from dpdk.org (dpdk.org [92.243.14.124]) by inbox.dpdk.org (Postfix) with ESMTP id 245F7A052B; Wed, 29 Jul 2020 15:28:40 +0200 (CEST) Received: from [92.243.14.124] (localhost [127.0.0.1]) by dpdk.org (Postfix) with ESMTP id 0327C10A3; Wed, 29 Jul 2020 15:28:40 +0200 (CEST) Received: from us-smtp-delivery-1.mimecast.com (us-smtp-1.mimecast.com [205.139.110.61]) by dpdk.org (Postfix) with ESMTP id 9F833F04 for ; Wed, 29 Jul 2020 15:28:38 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1596029318; 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: in-reply-to:in-reply-to:references:references; bh=j8q/Imi3gxRbZ362wbHWZCmLgGx7fzzyweYSz+gOEC4=; b=evLH2Ddku4NO/JKz29Htz7JaJ20xabJYe3Ycu4l4bJdKux7VjdFwJ/otHAAMrf/SZNWdan K4guo8Ea9duyepKvYwC2u52xaaPDLt1LYP1L0SWbHQ0RYwX8ojkNPL96imqoO33fOCRxBh E3YIX2Ap5K4aL1ynwuQyy97oQexjvx4= Received: from mail-ua1-f69.google.com (mail-ua1-f69.google.com [209.85.222.69]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-470-_rvh4UksOT2SyHGPQbiX6Q-1; Wed, 29 Jul 2020 09:28:36 -0400 X-MC-Unique: _rvh4UksOT2SyHGPQbiX6Q-1 Received: by mail-ua1-f69.google.com with SMTP id n4so7215115uaq.17 for ; Wed, 29 Jul 2020 06:28:36 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=j8q/Imi3gxRbZ362wbHWZCmLgGx7fzzyweYSz+gOEC4=; b=ExAUGOBWwYjeAi/9NG1JDEcn46FLR241q2qdhwNVV4P5GggZFoK6+r/QNfhpC4SH1N poHyf/BXR2ULoZ1mV4D1gzvAfkUIRlRiPZkvxombkDIjD7QyLk604BMw4sL3L9HY6GyC c0UAIwZvZeVEUdNFt3oUmoiP/wwyV1edUfFgVH6vGXbHYY1Ey52BIxfVM42eSMW3LRIh 6Y5lljG63fjOomApX7MArbVH6vf2UoEhNPMRrPzE77McVPGBk4BpYrPYfraBgscPGlWv zQvC8gwZukFso2lKdXkjKkmCPh+PAEUyAikIgOc60YdKsoWSjhULVPZosrbRDczNpmYl d8kg== X-Gm-Message-State: AOAM532K9/BtlNdHHe/Oyohj4r6Wy5zgTqFgVj55Eh6xovvTxn2NecUL D2yii2u5R5lRUStpbtVfEh9nWPWYml0+QB9kkIeasKldyZyaAOk8dT5K8zcW0huEdovE2BHFSnM ViFmWuiIY2fGZKgcfqfY= X-Received: by 2002:a1f:acc2:: with SMTP id v185mr22963037vke.18.1596029315690; Wed, 29 Jul 2020 06:28:35 -0700 (PDT) X-Google-Smtp-Source: ABdhPJwKVVxZoWunW4Q1Rr3fKhggiPcC+gMardVFAa5LxK4K9zrHrWmxLiBegxEZMbxSf/DJ2vf+suQFBUKclAhe044= X-Received: by 2002:a1f:acc2:: with SMTP id v185mr22963006vke.18.1596029315286; Wed, 29 Jul 2020 06:28:35 -0700 (PDT) MIME-Version: 1.0 References: <20200616162705.83575-1-ting.xu@intel.com> <20200722021628.17194-1-ting.xu@intel.com> In-Reply-To: From: David Marchand Date: Wed, 29 Jul 2020 15:28:24 +0200 Message-ID: To: "Dumitrescu, Cristian" Cc: "Xu, Ting" , dev , dpdk stable , Kevin Traynor , Luca Boccassi X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset="UTF-8" Subject: Re: [dpdk-dev] [dpdk-stable] [PATCH v4] lib/table: fix cache alignment issue X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces@dpdk.org Sender: "dev" On Wed, Jul 29, 2020 at 3:14 PM Dumitrescu, Cristian wrote: > > Please correct me if I am wrong, but it simply means this part of the > > table library never worked for 32-bit. > > It seems more adding 32-bit support rather than a fix and then I > > wonder if it has its place in rc3. > > > > Functionally. the code works, but performance is affected. > > The only thing that prevents the code from working is the check in the table create function that checks the size of the above structure is 64 bytes, which caught this issue. Yes, and that's my point. It was not working. It was not tested. This patch asks for backport in stable branches, I will let Kevin and Luca comment. > > > > > > > Now, looking at the details: > > > > For 64-bit on my x86, we have: > > > > struct rte_bucket_4_8 { > > uint64_t signature; /* 0 8 */ > > uint64_t lru_list; /* 8 8 */ > > struct rte_bucket_4_8 * next; /* 16 8 */ > > uint64_t next_valid; /* 24 8 */ > > uint64_t key[4]; /* 32 32 */ > > /* --- cacheline 1 boundary (64 bytes) --- */ > > uint8_t data[]; /* 64 0 */ > > > > /* size: 64, cachelines: 1, members: 6 */ > > }; > > > > > > For 32-bit, we have: > > > > struct rte_bucket_4_8 { > > uint64_t signature; /* 0 8 */ > > uint64_t lru_list; /* 8 8 */ > > struct rte_bucket_4_8 * next; /* 16 4 */ > > uint64_t next_valid; /* 20 8 */ > > uint64_t key[4]; /* 28 32 */ > > uint8_t data[]; /* 60 0 */ > > > > /* size: 60, cachelines: 1, members: 6 */ > > /* last cacheline: 60 bytes */ > > } __attribute__((__packed__)); > > > > ^^ it is interesting that a packed attribute ends up here. > > I saw no such attribute in the library code. > > Compiler black magic at work I guess... > > > > Where do you see the packet attribute? I don't see it in the code. That's pahole reporting this. Maybe the tool extrapolates this attribute based on the next_valid field placement... I don't know. > A packet attribute would explain this issue, i.e. why did the compiler decide not to insert an expected padfing of 4 bytes right after the "next" field, that would allow the field "next_valid" to be aligned to its natural boundary of 8 bytes. Or a 64-bit field on 32-bit has a special alignment that I am not aware of. > > > > > > > > > Fixes: 8aa327214c ("table: hash") > > > Cc: stable@dpdk.org > > > > > > Signed-off-by: Ting Xu > > > > > > --- > > > v3->v4: Change design based on comment > > > v2->v3: Rebase > > > v1->v2: Correct patch time > > > --- > > > lib/librte_table/rte_table_hash_key16.c | 17 +++++++++++++++++ > > > lib/librte_table/rte_table_hash_key32.c | 17 +++++++++++++++++ > > > lib/librte_table/rte_table_hash_key8.c | 16 ++++++++++++++++ > > > 3 files changed, 50 insertions(+) > > > > > > diff --git a/lib/librte_table/rte_table_hash_key16.c > > b/lib/librte_table/rte_table_hash_key16.c > > > index 2cca1c924..c4384b114 100644 > > > --- a/lib/librte_table/rte_table_hash_key16.c > > > +++ b/lib/librte_table/rte_table_hash_key16.c > > > @@ -33,6 +33,7 @@ > > > > > > #endif > > > > > > +#ifdef RTE_ARCH_64 > > > struct rte_bucket_4_16 { > > > /* Cache line 0 */ > > > uint64_t signature[4 + 1]; > > > @@ -46,6 +47,22 @@ struct rte_bucket_4_16 { > > > /* Cache line 2 */ > > > uint8_t data[0]; > > > }; > > > +#else > > > +struct rte_bucket_4_16 { > > > + /* Cache line 0 */ > > > + uint64_t signature[4 + 1]; > > > + uint64_t lru_list; > > > + struct rte_bucket_4_16 *next; > > > + uint32_t pad; > > > + uint64_t next_valid; > > > + > > > + /* Cache line 1 */ > > > + uint64_t key[4][2]; > > > + > > > + /* Cache line 2 */ > > > + uint8_t data[0]; > > > +}; > > > +#endif > > > > The change could simply be: > > > > @@ -38,6 +38,9 @@ struct rte_bucket_4_16 { > > uint64_t signature[4 + 1]; > > uint64_t lru_list; > > struct rte_bucket_4_16 *next; > > +#ifndef RTE_ARCH_64 > > + uint32_t pad; > > +#endif > > uint64_t next_valid; > > > > /* Cache line 1 */ > > > > It avoids duplicating the whole structure definition (we could miss > > updating one side of the #ifdef later). > > Idem for the other "8" and "32" structures. What about this comment? -- David Marchand