From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pa0-f67.google.com ([209.85.220.67]:34435 "EHLO mail-pa0-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751320AbcEKIPf (ORCPT ); Wed, 11 May 2016 04:15:35 -0400 Date: Tue, 10 May 2016 13:46:13 +0800 From: Simon Guo To: Shaohua Li Cc: linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, Steven Rostedt , axboe@fb.com, Kernel-team@fb.com Subject: Re: [PATCH 3/3] blk-throttle: don't parse cgroup path if trace isn't enabled Message-ID: <20160510054613.GA12366@simonLocalRHEL7.x64> References: <2c3ee532132f8925dd0be1178e8dee0bba6b448c.1462838969.git.shli@fb.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: Sender: linux-block-owner@vger.kernel.org List-Id: linux-block@vger.kernel.org Hi, On Mon, May 09, 2016 at 05:22:15PM -0700, Shaohua Li wrote: > if trace isn't enabled, parsing cgroup path just wastes cpu > > Signed-off-by: Shaohua Li > --- > block/blk-throttle.c | 5 ++--- > include/linux/blktrace_api.h | 9 +++++++++ > 2 files changed, 11 insertions(+), 3 deletions(-) > > diff --git a/block/blk-throttle.c b/block/blk-throttle.c > index 2149a1d..47a3e54 100644 > --- a/block/blk-throttle.c > +++ b/block/blk-throttle.c > @@ -211,15 +211,14 @@ static struct throtl_data *sq_to_td(struct throtl_service_queue *sq) > * > * The messages are prefixed with "throtl BLKG_NAME" if @sq belongs to a > * throtl_grp; otherwise, just "throtl". > - * > - * TODO: this should be made a function and name formatting should happen > - * after testing whether blktrace is enabled. > */ > #define throtl_log(sq, fmt, args...) do { \ > struct throtl_grp *__tg = sq_to_tg((sq)); \ > struct throtl_data *__td = sq_to_td((sq)); \ > \ > (void)__td; \ > + if (likely(!blk_trace_note_message_enabled(__td->queue))) \ > + break; \ > if ((__tg)) { \ > char __pbuf[128]; \ > \ > diff --git a/include/linux/blktrace_api.h b/include/linux/blktrace_api.h > index afc1343..0f3172b 100644 > --- a/include/linux/blktrace_api.h > +++ b/include/linux/blktrace_api.h > @@ -57,6 +57,14 @@ void __trace_note_message(struct blk_trace *, const char *fmt, ...); > } while (0) > #define BLK_TN_MAX_MSG 128 > > +static inline bool blk_trace_note_message_enabled(struct request_queue *q) > +{ > + struct blk_trace *bt = q->blk_trace; > + if (likely(!bt)) > + return false; > + return bt->act_mask & BLK_TC_NOTIFY; > +} Is there any reason to skip following condition? if (unlikely(bt->trace_state != Blktrace_running && !blk_tracer_enabled)) Thanks, - Simon