Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753236AbbLCSiJ (ORCPT ); Thu, 3 Dec 2015 13:38:09 -0500 Received: from mail-pf0-f182.google.com ([209.85.192.182]:35497 "EHLO mail-pf0-f182.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750873AbbLCSiH convert rfc822-to-8bit (ORCPT ); Thu, 3 Dec 2015 13:38:07 -0500 Content-Type: text/plain; charset=utf-8 Mime-Version: 1.0 (Mac OS X Mail 9.0 \(3094\)) Subject: Re: [PATCH 1/2] mm, printk: introduce new format string for flags From: yalin wang In-Reply-To: <87a8psq7r6.fsf@rasmusvillemoes.dk> Date: Thu, 3 Dec 2015 10:38:04 -0800 Cc: Vlastimil Babka , "open list:MEMORY MANAGEMENT" , linux-kernel , Andrew Morton , Joonsoo Kim , Minchan Kim , Sasha Levin , "Kirill A. Shutemov" , Mel Gorman , Michal Hocko Content-Transfer-Encoding: 8BIT Message-Id: <89A4C9BC-47F6-4768-8AA8-C1C4EFEFC52D@gmail.com> References: <20151125143010.GI27283@dhcp22.suse.cz> <1448899821-9671-1-git-send-email-vbabka@suse.cz> <4EAD2C33-D0E4-4DEB-92E5-9C0457E8635C@gmail.com> <565F5CD9.9080301@suse.cz> <1F60C207-1CC2-4B28-89AC-58C72D95A39D@gmail.com> <87a8psq7r6.fsf@rasmusvillemoes.dk> To: Rasmus Villemoes X-Mailer: Apple Mail (2.3094) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3040 Lines: 93 > On Dec 3, 2015, at 00:03, Rasmus Villemoes wrote: > > On Thu, Dec 03 2015, yalin wang wrote: > >>> On Dec 2, 2015, at 13:04, Vlastimil Babka wrote: >>> >>> On 12/02/2015 06:40 PM, yalin wang wrote: >>> >>> (please trim your reply next time, no need to quote whole patch here) >>> >>>> i am thinking why not make %pg* to be more generic ? >>>> not restricted to only GFP / vma flags / page flags . >>>> so could we change format like this ? >>>> define a flag spec struct to include flag and trace_print_flags and some other option : >>>> typedef struct { >>>> unsigned long flag; >>>> structtrace_print_flags *flags; >>>> unsigned long option; } flag_sec; >>>> flag_sec my_flag; >>>> in printk we only pass like this : >>>> printk(“%pg\n”, &my_flag) ; >>>> then it can print any flags defined by user . >>>> more useful for other drivers to use . >>> >>> I don't know, it sounds quite complicated > > Agreed, I think this would be premature generalization. There's also > some value in having the individual %pgX specifiers, as that allows > individual tweaks such as the mask_out for page flags. > > given that we had no flags printing >> if we use this generic method, %pgX where X can be used to specify some flag to mask out some thing . it will be great . > > Compared to printk("%pgv\n", &vma->flag), I know which I'd prefer to read. > >> i am not if DECLARE_FLAG_PRINTK_FMT and FLAG_PRINTK_FMT macro >> can be defined into one macro ? >> maybe need some trick here . >> >> is it possible ? > > Technically, I think the answer is yes, at least in C99 (and I suppose > gcc would accept it in gnu89 mode as well). > > printk("%pg\n", &(struct flag_printer){.flags = my_flags, .names = vmaflags_names}); > > Not tested, and I still don't think it would be particularly readable > even when macroized > > printk("%pg\n", PRINTF_VMAFLAGS(my_flags)); i test on gcc 4.9.3, it can work for this method, so the final solution like this: printk.h: struct flag_fmt_spec { unsigned long flag; struct trace_print_flags *flags; int array_size; char delimiter; } #define FLAG_FORMAT(flag, flag_array, delimiter) (&(struct flag_ft_spec){ .flag = flag, .flags = flag_array, .array_size = ARRAY_SIZE(flag_array), .delimiter = delimiter}) #define VMA_FLAG_FORMAT(flag) FLAG_FORMAT(flag, vmaflags_names, ‘|') source code: printk("%pg\n", VMA_FLAG_FORMAT(my_flags)); that’s all, see cpumask_pr_args(masks) macro, it also use macro and %*pb to print cpu mask . i think this method is not very complex to use . search source code , there is lots of printk to print flag into hex number : $ grep -n -r 'printk.*flag.*%x’ . it will be great if this flag string print is generic. Thanks -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/