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 54964C28D13 for ; Mon, 22 Aug 2022 18:28:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237423AbiHVS2M (ORCPT ); Mon, 22 Aug 2022 14:28:12 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52436 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237179AbiHVS2C (ORCPT ); Mon, 22 Aug 2022 14:28:02 -0400 Received: from out2.migadu.com (out2.migadu.com [IPv6:2001:41d0:2:aacc::]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3038C48E84; Mon, 22 Aug 2022 11:27:52 -0700 (PDT) Date: Mon, 22 Aug 2022 11:27:46 -0700 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1661192870; 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=859bRFvYP0PwP1RQEaN1BuNqPudeM49yRCMP2gzbo/M=; b=mCGQi+2b3AdYVcCk9kc+RYKSR5DNMp8IBmyH6G+E69Cq3b2l19KvwGFIuMAQgaZ1ip974E Gfuml2lG4ZQJmNqdc9vHZ1ompfYFjZdFzV0Xj/H73RUciXDYNcSERvs7e3WDbYpIjcVsB1 T0npKZERgo9FQlUXzHgUKV2CBE3OL1Y= X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Roman Gushchin To: Shakeel Butt Cc: Michal Hocko , Johannes Weiner , Muchun Song , Michal =?iso-8859-1?Q?Koutn=FD?= , Eric Dumazet , Soheil Hassas Yeganeh , Feng Tang , Oliver Sang , Andrew Morton , lkp@lists.01.org, Cgroups , Linux MM , netdev , LKML Subject: Re: [PATCH 2/3] mm: page_counter: rearrange struct page_counter fields Message-ID: References: <20220822001737.4120417-1-shakeelb@google.com> <20220822001737.4120417-3-shakeelb@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Migadu-Flow: FLOW_OUT X-Migadu-Auth-User: linux.dev Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Aug 22, 2022 at 09:04:59AM -0700, Shakeel Butt wrote: > On Mon, Aug 22, 2022 at 8:15 AM Michal Hocko wrote: > > > > On Mon 22-08-22 08:06:14, Shakeel Butt wrote: > > [...] > > > > > struct page_counter { > > > > > + /* > > > > > + * Make sure 'usage' does not share cacheline with any other field. The > > > > > + * memcg->memory.usage is a hot member of struct mem_cgroup. > > > > > + */ > > > > > + PC_PADDING(_pad1_); > > > > > > > > Why don't you simply require alignment for the structure? > > > > > > I don't just want the alignment of the structure. I want different > > > fields of this structure to not share the cache line. More > > > specifically the 'high' and 'usage' fields. With this change the usage > > > will be its own cache line, the read-most fields will be on separate > > > cache line and the fields which sometimes get updated on charge path > > > based on some condition will be a different cache line from the > > > previous two. > > > > I do not follow. If you make an explicit requirement for the structure > > alignement then the first field in the structure will be guarantied to > > have that alignement and you achieve the rest to be in the other cache > > line by adding padding behind that. > > Oh, you were talking explicitly about _pad1_, yes, we can remove it > and make the struct cache align. I will do it in the next version. Yes, please, it caught my eyes too. With this change: Acked-by: Roman Gushchin Also, can you, please, include the numbers on the additional memory overhead? I think it still worth it, just think we need to include them for a record. Thanks! From mboxrd@z Thu Jan 1 00:00:00 1970 Content-Type: multipart/mixed; boundary="===============5552283602482310354==" MIME-Version: 1.0 From: Roman Gushchin To: lkp@lists.01.org Subject: Re: [PATCH 2/3] mm: page_counter: rearrange struct page_counter fields Date: Mon, 22 Aug 2022 11:27:46 -0700 Message-ID: In-Reply-To: List-Id: --===============5552283602482310354== Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable On Mon, Aug 22, 2022 at 09:04:59AM -0700, Shakeel Butt wrote: > On Mon, Aug 22, 2022 at 8:15 AM Michal Hocko wrote: > > > > On Mon 22-08-22 08:06:14, Shakeel Butt wrote: > > [...] > > > > > struct page_counter { > > > > > + /* > > > > > + * Make sure 'usage' does not share cacheline with any othe= r field. The > > > > > + * memcg->memory.usage is a hot member of struct mem_cgroup. > > > > > + */ > > > > > + PC_PADDING(_pad1_); > > > > > > > > Why don't you simply require alignment for the structure? > > > > > > I don't just want the alignment of the structure. I want different > > > fields of this structure to not share the cache line. More > > > specifically the 'high' and 'usage' fields. With this change the usage > > > will be its own cache line, the read-most fields will be on separate > > > cache line and the fields which sometimes get updated on charge path > > > based on some condition will be a different cache line from the > > > previous two. > > > > I do not follow. If you make an explicit requirement for the structure > > alignement then the first field in the structure will be guarantied to > > have that alignement and you achieve the rest to be in the other cache > > line by adding padding behind that. > = > Oh, you were talking explicitly about _pad1_, yes, we can remove it > and make the struct cache align. I will do it in the next version. Yes, please, it caught my eyes too. With this change: Acked-by: Roman Gushchin Also, can you, please, include the numbers on the additional memory overhea= d? I think it still worth it, just think we need to include them for a record. Thanks! --===============5552283602482310354==-- From mboxrd@z Thu Jan 1 00:00:00 1970 From: Roman Gushchin Subject: Re: [PATCH 2/3] mm: page_counter: rearrange struct page_counter fields Date: Mon, 22 Aug 2022 11:27:46 -0700 Message-ID: References: <20220822001737.4120417-1-shakeelb@google.com> <20220822001737.4120417-3-shakeelb@google.com> Mime-Version: 1.0 Return-path: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1661192870; 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=859bRFvYP0PwP1RQEaN1BuNqPudeM49yRCMP2gzbo/M=; b=mCGQi+2b3AdYVcCk9kc+RYKSR5DNMp8IBmyH6G+E69Cq3b2l19KvwGFIuMAQgaZ1ip974E Gfuml2lG4ZQJmNqdc9vHZ1ompfYFjZdFzV0Xj/H73RUciXDYNcSERvs7e3WDbYpIjcVsB1 T0npKZERgo9FQlUXzHgUKV2CBE3OL1Y= Content-Disposition: inline In-Reply-To: List-ID: Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Shakeel Butt Cc: Michal Hocko , Johannes Weiner , Muchun Song , Michal =?iso-8859-1?Q?Koutn=FD?= , Eric Dumazet , Soheil Hassas Yeganeh , Feng Tang , Oliver Sang , Andrew Morton , lkp-hn68Rpc1hR1g9hUCZPvPmw@public.gmane.org, Cgroups , Linux MM , netdev , LKML On Mon, Aug 22, 2022 at 09:04:59AM -0700, Shakeel Butt wrote: > On Mon, Aug 22, 2022 at 8:15 AM Michal Hocko wrote: > > > > On Mon 22-08-22 08:06:14, Shakeel Butt wrote: > > [...] > > > > > struct page_counter { > > > > > + /* > > > > > + * Make sure 'usage' does not share cacheline with any other field. The > > > > > + * memcg->memory.usage is a hot member of struct mem_cgroup. > > > > > + */ > > > > > + PC_PADDING(_pad1_); > > > > > > > > Why don't you simply require alignment for the structure? > > > > > > I don't just want the alignment of the structure. I want different > > > fields of this structure to not share the cache line. More > > > specifically the 'high' and 'usage' fields. With this change the usage > > > will be its own cache line, the read-most fields will be on separate > > > cache line and the fields which sometimes get updated on charge path > > > based on some condition will be a different cache line from the > > > previous two. > > > > I do not follow. If you make an explicit requirement for the structure > > alignement then the first field in the structure will be guarantied to > > have that alignement and you achieve the rest to be in the other cache > > line by adding padding behind that. > > Oh, you were talking explicitly about _pad1_, yes, we can remove it > and make the struct cache align. I will do it in the next version. Yes, please, it caught my eyes too. With this change: Acked-by: Roman Gushchin Also, can you, please, include the numbers on the additional memory overhead? I think it still worth it, just think we need to include them for a record. Thanks!