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 F326FC54EE9 for ; Thu, 22 Sep 2022 21:43:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231183AbiIVVn4 (ORCPT ); Thu, 22 Sep 2022 17:43:56 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43226 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231387AbiIVVnq (ORCPT ); Thu, 22 Sep 2022 17:43:46 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7504F36405 for ; Thu, 22 Sep 2022 14:43:45 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1663883024; 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: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=sSNEFy5b6cxFiax24pzuCPv8XiqsovfHI3ee7mzmuwA=; b=eK/lQdQVtSEX6/VcwNIVU1W7S6foCuKrNcsYJtP925RClE2g8GsNbrtQh8ZG1imKGepLT+ Pm2/qfZaXGHo7tE8Zyp/eM6U4EJ1U6XJossA9zDDy8k7CWOrIEExEecPMBwBwZDA2GOu75 9ruoDaNI4Hx/C8x0/NsfkkHwD9scrDs= Received: from mimecast-mx02.redhat.com (mx3-rdu2.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-50-jSTf65OiPnqhHnoJULZfiw-1; Thu, 22 Sep 2022 17:43:41 -0400 X-MC-Unique: jSTf65OiPnqhHnoJULZfiw-1 Received: from smtp.corp.redhat.com (int-mx09.intmail.prod.int.rdu2.redhat.com [10.11.54.9]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id E334D294EDF5; Thu, 22 Sep 2022 21:43:40 +0000 (UTC) Received: from lorien.usersys.redhat.com (unknown [10.22.33.123]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 8547347505E; Thu, 22 Sep 2022 21:43:40 +0000 (UTC) Date: Thu, 22 Sep 2022 17:43:38 -0400 From: Phil Auld To: Yury Norov Cc: Andy Shevchenko , linux-kernel@vger.kernel.org, Rasmus Villemoes , Petr =?utf-8?Q?=C5=A0tetiar?= , Greg Kroah-Hartman Subject: Re: [PATCH v2 1/1] cpumask: Don't waste memory for sysfs cpulist nodes Message-ID: References: <20220922194954.1078-1-andriy.shevchenko@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-Scanned-By: MIMEDefang 3.1 on 10.11.54.9 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Sep 22, 2022 at 01:41:40PM -0700 Yury Norov wrote: > + Petr Štetiar , > + Greg Kroah-Hartman > > On Thu, Sep 22, 2022 at 10:49:54PM +0300, Andy Shevchenko wrote: > > Currently the approximation is used which wastes the more memory > > the more CPUs are present on the system. Proposed change calculates > > the exact maximum needed in the worst case: > > > > NR_CPUS old new > > ------- --- --- > > 1 .. 1170 4096 4096 > > 1171 .. 1860 4098 .. 6510 4096 > > ... ... ... > > 2*4096 28672 19925 > > 4*4096 57344 43597 > > 8*4096 114688 92749 > > 16*4096 229376 191053 > > 32*4096 458752 403197 > > 64*4096 917504 861949 > > 128*4096 1835008 1779453 > > 256*4096 3670016 3670016 > > > > Under the hood the reccurent formula is being used: > > (5 - 0) * 2 + > > (50 - 5) * 3 + > > (500 - 50) * 4 + > > (5000 - 500) * 5 + > > ... > > (X[i] - X[i-1]) * i > > > > which allows to count the exact maximum length in the worst case, > > i.e. when each second CPU is being listed. For backward compatibility > > for more than 1170 and less than 1861 CPUs the page size is preserved. > > > > For less than 1171 and more than 1 million CPUs the old is being used. > > 1861 > > > > > Signed-off-by: Andy Shevchenko > > --- > > v2: described better the advantage for 1171..1860 CPUs cases > > include/linux/cpumask.h | 48 +++++++++++++++++++++++++++++++++++++++++ > > 1 file changed, 48 insertions(+) > > > > diff --git a/include/linux/cpumask.h b/include/linux/cpumask.h > > index 1b442fb2001f..12cf0905ca74 100644 > > --- a/include/linux/cpumask.h > > +++ b/include/linux/cpumask.h > > @@ -1122,6 +1122,21 @@ cpumap_print_list_to_buf(char *buf, const struct cpumask *mask, > > * > > * for cpumap NR_CPUS * 9/32 - 1 should be an exact length. > > * > > + * for cpulist the reccurent formula is being used: > > + * (5 - 0) * 2 + > > + * (50 - 5) * 3 + > > + * (500 - 50) * 4 + > > + * (5000 - 500) * 5 + > > + * ... > > + * (X[i] - X[i-1]) * i > > + * > > + * which allows to count the exact maximum length in the worst case, > > + * i.e. when each second CPU is being listed. For backward compatibility > > + * for more than 1170 and less than 1861 CPUs the page size is preserved. > > + * > > + * For less than 1171 and more than 1 million CPUs the old is being used > > + * as described below: > > + * > > * For cpulist 7 is (ceil(log10(NR_CPUS)) + 1) allowing for NR_CPUS to be up > > * to 2 orders of magnitude larger than 8192. And then we divide by 2 to > > * cover a worst-case of every other cpu being on one of two nodes for a > > @@ -1132,6 +1147,39 @@ cpumap_print_list_to_buf(char *buf, const struct cpumask *mask, > > */ > > #define CPUMAP_FILE_MAX_BYTES (((NR_CPUS * 9)/32 > PAGE_SIZE) \ > > ? (NR_CPUS * 9)/32 - 1 : PAGE_SIZE) > > + > > +#define __CPULIST_FOR_10(x) (((x + 1) / 2 - 0) * 2) > > +#define __CPULIST_FOR_100(x) (((x + 1) / 2 - 5) * 3) > > +#define __CPULIST_FOR_1000(x) (((x + 1) / 2 - 50) * 4) > > +#define __CPULIST_FOR_10000(x) (((x + 1) / 2 - 500) * 5) > > +#define __CPULIST_FOR_100000(x) (((x + 1) / 2 - 5000) * 6) > > +#define __CPULIST_FOR_1000000(x) (((x + 1) / 2 - 50000) * 7) > > The defs below will be nicer if you make it like this: > > #define __CPULIST_FOR_10(x) (((x + 1) / 2 - 0) * 2) > #define __CPULIST_FOR_100(x) __CPULIST_FOR_10(10) + (((x + 1) / 2 - 5) * 3) > #define __CPULIST_FOR_1000(x) __CPULIST_FOR_100(100) + (((x + 1) / 2 - 50) * 4) > ... > > > > > +#if NR_CPUS < 1861 > > +#define CPULIST_FILE_MAX_BYTES PAGE_SIZE > > The comment says: > for more than 1170 and less than 1861 CPUs the page size is preserved. > > Which doesn't look correct. Looks like it should be: > for less than 1861 CPUs the page size is preserved. > > Or I miss something? > > > +#elif NR_CPUS < 10000 > > +#define CPULIST_FILE_MAX_BYTES \ > > + (__CPULIST_FOR_10(10) + \ > > + __CPULIST_FOR_100(100) + \ > > + __CPULIST_FOR_1000(1000) + \ > > + __CPULIST_FOR_10000(NR_CPUS)) > > +#elif NR_CPUS < 100000 > > +#define CPULIST_FILE_MAX_BYTES \ > > + (__CPULIST_FOR_10(10) + \ > > + __CPULIST_FOR_100(100) + \ > > + __CPULIST_FOR_1000(1000) + \ > > + __CPULIST_FOR_10000(10000) + \ > > + __CPULIST_FOR_100000(NR_CPUS)) > > +#elif NR_CPUS < 1000000 > > +#define CPULIST_FILE_MAX_BYTES \ > > + (__CPULIST_FOR_10(10) + \ > > + __CPULIST_FOR_100(100) + \ > > + __CPULIST_FOR_1000(1000) + \ > > + __CPULIST_FOR_10000(10000) + \ > > + __CPULIST_FOR_100000(100000) + \ > > + __CPULIST_FOR_1000000(NR_CPUS)) > > +#else > > #define CPULIST_FILE_MAX_BYTES (((NR_CPUS * 7)/2 > PAGE_SIZE) ? (NR_CPUS * 7)/2 : PAGE_SIZE) > > +#endif > > > > #endif /* __LINUX_CPUMASK_H */ > > -- > > 2.35.1 > > I'm OK to take this in replace for Phil's version, but the commit that > introduces CPULIST_FILE_MAX_BYTES is already in mainline: 7ee951acd31a8 > ("drivers/base: fix userspace break from using bin_attributes for cpumap > and cpulist"). Can you rebase it on top of v6.0-rc6? > > Greg, since Andy's version is more precise, I'd like to send a pull > request with it in -rc7. Can you drop Phil's patch so I'll go with > this one? > This changes the other of the 2 macros and looks like it is already on top of the fix to CPUMAP_FILE_MAX_BYTES. It should be able to go right on top of a tree with that one in it, I think. With the comment fixed up as you note above I'll git Reviewed-by: and Tested-by: shortly. This one is a refinement of 7ee951acd31a8 though and is not a critical as the one Greg was talking about and Petr hit. Cheers, Phil > Thanks, > Yury > --