Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754088AbbLJEE7 (ORCPT ); Wed, 9 Dec 2015 23:04:59 -0500 Received: from cdptpa-outbound-snat.email.rr.com ([107.14.166.228]:6914 "EHLO cdptpa-oedge-vip.email.rr.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1752655AbbLJEE6 (ORCPT ); Wed, 9 Dec 2015 23:04:58 -0500 Date: Wed, 9 Dec 2015 23:04:56 -0500 From: Steven Rostedt To: Joonsoo Kim Cc: Vlastimil Babka , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Andrew Morton , Minchan Kim , Sasha Levin , "Kirill A. Shutemov" , Mel Gorman , Michal Hocko , Rasmus Villemoes Subject: Re: [PATCH v2 1/3] mm, printk: introduce new format string for flags Message-ID: <20151210040456.GC7814@home.goodmis.org> References: <87io4hi06n.fsf@rasmusvillemoes.dk> <1449242195-16374-1-git-send-email-vbabka@suse.cz> <20151210025944.GB17967@js1304-P5Q-DELUXE> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20151210025944.GB17967@js1304-P5Q-DELUXE> User-Agent: Mutt/1.5.24 (2015-08-30) X-RR-Connecting-IP: 107.14.168.130:25 X-Cloudmark-Score: 0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2590 Lines: 57 On Thu, Dec 10, 2015 at 11:59:44AM +0900, Joonsoo Kim wrote: > Ccing, Steven to ask trace-cmd problem. Thanks, I should have been Cc'd for the rest as well. > > On Fri, Dec 04, 2015 at 04:16:33PM +0100, Vlastimil Babka wrote: > > In mm we use several kinds of flags bitfields that are sometimes printed for > > debugging purposes, or exported to userspace via sysfs. To make them easier to > > interpret independently on kernel version and config, we want to dump also the > > symbolic flag names. So far this has been done with repeated calls to > > pr_cont(), which is unreliable on SMP, and not usable for e.g. sysfs export. > > > > To get a more reliable and universal solution, this patch extends printk() > > format string for pointers to handle the page flags (%pgp), gfp_flags (%pgg) > > and vma flags (%pgv). Existing users of dump_flag_names() are converted and > > simplified. > > > > It would be possible to pass flags by value instead of pointer, but the %p > > format string for pointers already has extensions for various kernel > > structures, so it's a good fit, and the extra indirection in a non-critical > > path is negligible. > > I'd like to use %pgp in tracepoint output. It works well when I do > 'cat /sys/kernel/debug/tracing/trace' but not works well when I do > './trace-cmd report'. It prints following error log. > > [page_ref:page_ref_unfreeze] bad op token & > [page_ref:page_ref_set] bad op token & > [page_ref:page_ref_mod_unless] bad op token & > [page_ref:page_ref_mod_and_test] bad op token & > [page_ref:page_ref_mod_and_return] bad op token & > [page_ref:page_ref_mod] bad op token & > [page_ref:page_ref_freeze] bad op token & > > Following is the format I used. > > TP_printk("pfn=0x%lx flags=%pgp count=%d mapcount=%d mapping=%p mt=%d val=%d ret=%d", > __entry->pfn, &__entry->flags, __entry->count, > __entry->mapcount, __entry->mapping, __entry->mt, > __entry->val, __entry->ret) > > Could it be solved by 'trace-cmd' itself? > Or it's better to pass flags by value? > Or should I use something like show_gfp_flags()? Yes this can be solved in perf and trace-cmd via the parse-events.c file. And as soon as that happens, whatever method we decide upon becomes a userspace ABI. So don't think you can change it later. -- Steve -- 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/