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 54092C433EF for ; Thu, 7 Jul 2022 01:36:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234887AbiGGBgN (ORCPT ); Wed, 6 Jul 2022 21:36:13 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:38850 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234799AbiGGBgL (ORCPT ); Wed, 6 Jul 2022 21:36:11 -0400 Received: from mailgw02.mediatek.com (unknown [210.61.82.184]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 56F672E9FB for ; Wed, 6 Jul 2022 18:36:10 -0700 (PDT) X-UUID: 4465504833be49d8ba0e630c2736963d-20220707 X-CID-P-RULE: Release_Ham X-CID-O-INFO: VERSION:1.1.8,REQID:b565b9fd-64d9-4d41-95c9-38c3bcedf148,OB:0,LO B:0,IP:0,URL:5,TC:0,Content:0,EDM:0,RT:0,SF:0,FILE:0,RULE:Release_Ham,ACTI ON:release,TS:5 X-CID-META: VersionHash:0f94e32,CLOUDID:1769cfd6-5d6d-4eaf-a635-828a3ee48b7c,C OID:IGNORED,Recheck:0,SF:nil,TC:nil,Content:0,EDM:-3,IP:nil,URL:1,File:nil ,QS:nil,BEC:nil,COL:0 X-UUID: 4465504833be49d8ba0e630c2736963d-20220707 Received: from mtkexhb02.mediatek.inc [(172.21.101.103)] by mailgw02.mediatek.com (envelope-from ) (Generic MTA with TLSv1.2 ECDHE-RSA-AES256-SHA384 256/256) with ESMTP id 2093498817; Thu, 07 Jul 2022 09:36:06 +0800 Received: from mtkmbs11n2.mediatek.inc (172.21.101.187) by mtkmbs11n2.mediatek.inc (172.21.101.187) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.792.3; Thu, 7 Jul 2022 09:36:05 +0800 Received: from mhfsdcap04 (10.17.3.154) by mtkmbs11n2.mediatek.inc (172.21.101.73) with Microsoft SMTP Server id 15.2.792.3 via Frontend Transport; Thu, 7 Jul 2022 09:35:58 +0800 Message-ID: <76e12594cf81b57c98e536c68b2947f9ed0a4296.camel@mediatek.com> Subject: Re: [PATCH 01/13] tracing/events: Add __vstring() and __assign_vstr() helper macros From: Chunfeng Yun To: Steven Rostedt , CC: Ingo Molnar , Andrew Morton , Dennis Dalessandro , Jason Gunthorpe , Leon Romanovsky , Kalle Valo , "David S. Miller" , Eric Dumazet , "Jakub Kicinski" , Paolo Abeni , "Arend van Spriel" , Franky Lin , "Hante Meuleman" , Gregory Greenman , Peter Chen , "Greg Kroah-Hartman" , Mathias Nyman , Bin Liu , Marek Lindner , Simon Wunderlich , Antonio Quartulli , Sven Eckelmann , Johannes Berg , Jim Cromie Date: Thu, 7 Jul 2022 09:35:53 +0800 In-Reply-To: <20220705224749.053570613@goodmis.org> References: <20220705224453.120955146@goodmis.org> <20220705224749.053570613@goodmis.org> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.28.5-0ubuntu0.18.04.2 MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-MTK: N Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 2022-07-05 at 18:44 -0400, Steven Rostedt wrote: > From: "Steven Rostedt (Google)" > > There's several places that open code the following logic: > > TP_STRUCT__entry(__dynamic_array(char, msg, MSG_MAX)), > TP_fast_assign(vsnprintf(__get_str(msg), MSG_MAX, vaf->fmt, *vaf- > >va);) > > To load a string created by variable array va_list. > > The main issue with this approach is that "MSG_MAX" usage in the > __dynamic_array() portion. That actually just reserves the MSG_MAX in > the > event, and even wastes space because there's dynamic meta data also > saved > in the event to denote the offset and size of the dynamic array. It > would > have been better to just use a static __array() field. > > Instead, create __vstring() and __assign_vstr() that work like > __string > and __assign_str() but instead of taking a destination string to > copy, > take a format string and a va_list pointer and fill in the values. > > It uses the helper: > > #define __trace_event_vstr_len(fmt, va) \ > ({ \ > va_list __ap; \ > int __ret; \ > \ > va_copy(__ap, *(va)); \ > __ret = vsnprintf(NULL, 0, fmt, __ap); \ > va_end(__ap); \ > \ > min(__ret, TRACE_EVENT_STR_MAX); \ > }) > > To figure out the length to store the string. It may be slightly > slower as > it needs to run the vsnprintf() twice, but it now saves space on the > ring > buffer. > > Cc: Dennis Dalessandro > Cc: Jason Gunthorpe > Cc: Leon Romanovsky > Cc: Kalle Valo > Cc: "David S. Miller" > Cc: Eric Dumazet > Cc: Jakub Kicinski > Cc: Paolo Abeni > Cc: Arend van Spriel > Cc: Franky Lin > Cc: Hante Meuleman > Cc: Gregory Greenman > Cc: Peter Chen > Cc: Greg Kroah-Hartman > Cc: Mathias Nyman > Cc: Chunfeng Yun > Cc: Bin Liu > Cc: Marek Lindner > Cc: Simon Wunderlich > Cc: Antonio Quartulli > Cc: Sven Eckelmann > Cc: Johannes Berg > Cc: Jim Cromie > Signed-off-by: Steven Rostedt (Google) Seems difficult to get this patch without, such as, '--cc=" linux-kernel@vger.kernel.org"' > --- > include/linux/trace_events.h | 18 ++++++++++++++++++ > include/trace/stages/stage1_struct_define.h | 3 +++ > include/trace/stages/stage2_data_offsets.h | 3 +++ > include/trace/stages/stage4_event_fields.h | 3 +++ > include/trace/stages/stage5_get_offsets.h | 4 ++++ > include/trace/stages/stage6_event_callback.h | 7 +++++++ > 6 files changed, 38 insertions(+) > > diff --git a/include/linux/trace_events.h > b/include/linux/trace_events.h > index e6e95a9f07a5..e6f8ba52a958 100644 > --- a/include/linux/trace_events.h > +++ b/include/linux/trace_events.h > @@ -916,6 +916,24 @@ perf_trace_buf_submit(void *raw_data, int size, > int rctx, u16 type, > > #endif > > +#define TRACE_EVENT_STR_MAX 512 > + > +/* > + * gcc warns that you can not use a va_list in an inlined > + * function. But lets me make it into a macro :-/ > + */ > +#define __trace_event_vstr_len(fmt, va) \ > +({ \ > + va_list __ap; \ > + int __ret; \ > + \ > + va_copy(__ap, *(va)); \ > + __ret = vsnprintf(NULL, 0, fmt, __ap); \ > + va_end(__ap); \ > + \ > + min(__ret, TRACE_EVENT_STR_MAX); \ > +}) > + > #endif /* _LINUX_TRACE_EVENT_H */ > > /* > diff --git a/include/trace/stages/stage1_struct_define.h > b/include/trace/stages/stage1_struct_define.h > index a16783419687..1b7bab60434c 100644 > --- a/include/trace/stages/stage1_struct_define.h > +++ b/include/trace/stages/stage1_struct_define.h > @@ -26,6 +26,9 @@ > #undef __string_len > #define __string_len(item, src, len) __dynamic_array(char, item, -1) > > +#undef __vstring > +#define __vstring(item, fmt, ap) __dynamic_array(char, item, -1) > + > #undef __bitmask > #define __bitmask(item, nr_bits) __dynamic_array(char, item, -1) > > diff --git a/include/trace/stages/stage2_data_offsets.h > b/include/trace/stages/stage2_data_offsets.h > index 42fd1e8813ec..1b7a8f764fdd 100644 > --- a/include/trace/stages/stage2_data_offsets.h > +++ b/include/trace/stages/stage2_data_offsets.h > @@ -32,6 +32,9 @@ > #undef __string_len > #define __string_len(item, src, len) __dynamic_array(char, item, -1) > > +#undef __vstring > +#define __vstring(item, fmt, ap) __dynamic_array(char, item, -1) > + > #undef __bitmask > #define __bitmask(item, nr_bits) __dynamic_array(unsigned long, > item, -1) > > diff --git a/include/trace/stages/stage4_event_fields.h > b/include/trace/stages/stage4_event_fields.h > index e80cdc397a43..c3790ec7a453 100644 > --- a/include/trace/stages/stage4_event_fields.h > +++ b/include/trace/stages/stage4_event_fields.h > @@ -38,6 +38,9 @@ > #undef __string_len > #define __string_len(item, src, len) __dynamic_array(char, item, -1) > > +#undef __vstring > +#define __vstring(item, fmt, ap) __dynamic_array(char, item, -1) > + > #undef __bitmask > #define __bitmask(item, nr_bits) __dynamic_array(unsigned long, > item, -1) > > diff --git a/include/trace/stages/stage5_get_offsets.h > b/include/trace/stages/stage5_get_offsets.h > index 7ee5931300e6..fba4c24ed9e6 100644 > --- a/include/trace/stages/stage5_get_offsets.h > +++ b/include/trace/stages/stage5_get_offsets.h > @@ -39,6 +39,10 @@ > #undef __string_len > #define __string_len(item, src, len) __dynamic_array(char, item, > (len) + 1) > > +#undef __vstring > +#define __vstring(item, fmt, ap) __dynamic_array(char, item, > \ > + __trace_event_vstr_len(fmt, ap)) > + > #undef __rel_dynamic_array > #define __rel_dynamic_array(type, item, len) > \ > __item_length = (len) * sizeof(type); > \ > diff --git a/include/trace/stages/stage6_event_callback.h > b/include/trace/stages/stage6_event_callback.h > index e1724f73594b..0f51f6b3ab70 100644 > --- a/include/trace/stages/stage6_event_callback.h > +++ b/include/trace/stages/stage6_event_callback.h > @@ -24,6 +24,9 @@ > #undef __string_len > #define __string_len(item, src, len) __dynamic_array(char, item, -1) > > +#undef __vstring > +#define __vstring(item, fmt, ap) __dynamic_array(char, item, -1) > + > #undef __assign_str > #define __assign_str(dst, src) > \ > strcpy(__get_str(dst), (src) ? (const char *)(src) : "(null)"); > @@ -35,6 +38,10 @@ > __get_str(dst)[len] = '\0'; > \ > } while(0) > > +#undef __assign_vstr > +#define __assign_vstr(dst, fmt, va) > \ > + vsnprintf(__get_str(dst), TRACE_EVENT_STR_MAX, fmt, *(va)) > + > #undef __bitmask > #define __bitmask(item, nr_bits) __dynamic_array(unsigned long, > item, -1) >