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 B1C8AC433F5 for ; Fri, 11 Mar 2022 23:55:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229828AbiCKX4i (ORCPT ); Fri, 11 Mar 2022 18:56:38 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50676 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229808AbiCKX4h (ORCPT ); Fri, 11 Mar 2022 18:56:37 -0500 Received: from linux.microsoft.com (linux.microsoft.com [13.77.154.182]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 225EFD81; Fri, 11 Mar 2022 15:55:33 -0800 (PST) Received: from kbox (c-73-140-2-214.hsd1.wa.comcast.net [73.140.2.214]) by linux.microsoft.com (Postfix) with ESMTPSA id AEEBD20B7178; Fri, 11 Mar 2022 15:55:32 -0800 (PST) DKIM-Filter: OpenDKIM Filter v2.11.0 linux.microsoft.com AEEBD20B7178 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.microsoft.com; s=default; t=1647042932; bh=6ZrDSYmvOkJ2v9dCqiXvjF1J0+mtHZ+4Ek2KC4gi76A=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=LmGw75nB1upmYXQfSTaJS2g/obC5mRoX6+8DlI2WGujX4olHKXtaqL5YU5rcfXCb7 O8UTDNYG9RoZvKlIPyV9w8wVAseYw/UDgPGdKgyCDIAD4NYWGbwVNHhw7c36XkFWaw iKyuvTGGv/gyxPlSg57S4R2uQtYB4EWFx+arVAuI= Date: Fri, 11 Mar 2022 15:55:30 -0800 From: Beau Belgrave To: Steven Rostedt Cc: mhiramat@kernel.org, anders.roxell@linaro.org, linux-trace-devel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-next@vger.kernel.org Subject: Re: [PATCH] user_events: Use alloc_pages instead of kzalloc for register pages Message-ID: <20220311235530.GB2101@kbox> References: <20220311223028.1865-1-beaub@linux.microsoft.com> <20220311183343.4d8c94a5@gandalf.local.home> <20220311184440.537e9f83@gandalf.local.home> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220311184440.537e9f83@gandalf.local.home> User-Agent: Mutt/1.9.4 (2018-02-28) Precedence: bulk List-ID: X-Mailing-List: linux-trace-devel@vger.kernel.org On Fri, Mar 11, 2022 at 06:44:40PM -0500, Steven Rostedt wrote: > On Fri, 11 Mar 2022 18:33:43 -0500 > Steven Rostedt wrote: > > > I tried it slightly differently. Why waist bits if MAX_EVENTS is greater > > than the order. That is, make MAX_EVENTS depend on the order, not the other > > way around. > > Here's a version that keeps the reserving part as well as some bug fixes (I > didn't even compile the previous version ;-) > > -- Steve > > diff --git a/kernel/trace/trace_events_user.c b/kernel/trace/trace_events_user.c > index 4febc1d6ae72..e10ad057e797 100644 > --- a/kernel/trace/trace_events_user.c > +++ b/kernel/trace/trace_events_user.c > @@ -30,9 +30,10 @@ > > /* > * Limits how many trace_event calls user processes can create: > - * Must be multiple of PAGE_SIZE. > + * Must be a power of two of PAGE_SIZE. > */ > -#define MAX_PAGES 1 > +#define MAX_PAGE_ORDER 0 > +#define MAX_PAGES (1 << MAX_PAGE_ORDER) > #define MAX_EVENTS (MAX_PAGES * PAGE_SIZE) > > /* Limit how long of an event name plus args within the subsystem. */ > @@ -1622,16 +1623,17 @@ static void set_page_reservations(bool set) > > static int __init trace_events_user_init(void) > { > + struct page *pages; > int ret; > > /* Zero all bits beside 0 (which is reserved for failures) */ > bitmap_zero(page_bitmap, MAX_EVENTS); > set_bit(0, page_bitmap); > > - register_page_data = kzalloc(MAX_EVENTS, GFP_KERNEL); > - > - if (!register_page_data) > + pages = alloc_pages(GFP_KERNEL | __GFP_ZERO, MAX_PAGE_ORDER); > + if (!pages) > return -ENOMEM; > + register_page_data = page_address(pages); > > set_page_reservations(true); > > @@ -1640,7 +1642,7 @@ static int __init trace_events_user_init(void) > if (ret) { > pr_warn("user_events could not register with tracefs\n"); > set_page_reservations(false); > - kfree(register_page_data); > + __free_pages(pages, MAX_PAGE_ORDER); > return ret; > } > This looks good to me, I agree having the max events aligning to page order makes more sense going forward. Thanks, -Beau