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Fri, 30 Aug 2019 11:26:46 GMT Received: from aserv0122.oracle.com (aserv0122.oracle.com [141.146.126.236]) by aserp3020.oracle.com with ESMTP id 2upc8xbmce-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Fri, 30 Aug 2019 11:26:46 +0000 Received: from abhmp0004.oracle.com (abhmp0004.oracle.com [141.146.116.10]) by aserv0122.oracle.com (8.14.4/8.14.4) with ESMTP id x7UBQhS3007665; Fri, 30 Aug 2019 11:26:43 GMT Received: from kadam (/41.57.98.10) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Fri, 30 Aug 2019 04:26:43 -0700 Date: Fri, 30 Aug 2019 14:26:12 +0300 From: Dan Carpenter To: Gao Xiang Cc: devel@driverdev.osuosl.org, Sasha Levin , Valdis =?utf-8?Q?Kl=C4=93tnieks?= , Greg Kroah-Hartman , linux-kernel@vger.kernel.org, Christoph Hellwig , linux-fsdevel@vger.kernel.org, OGAWA Hirofumi Subject: Re: [PATCH] staging: exfat: add exfat filesystem code to staging Message-ID: <20190830112612.GF8372@kadam> References: <20190829095019.GA13557@kroah.com> <20190829103749.GA13661@infradead.org> <20190829111810.GA23393@kroah.com> <20190829151144.GJ23584@kadam> <20190829152757.GA125003@architecture4> <20190829154346.GK23584@kadam> <20190829155127.GA136563@architecture4> <20190829160441.GA141079@architecture4> <20190830083445.GL23584@kadam> <20190830084333.GA193084@architecture4> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190830084333.GA193084@architecture4> User-Agent: Mutt/1.9.4 (2018-02-28) X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9364 signatures=668685 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 suspectscore=2 malwarescore=0 phishscore=0 bulkscore=0 spamscore=0 mlxscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1906280000 definitions=main-1908300124 X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9364 signatures=668685 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 priorityscore=1501 malwarescore=0 suspectscore=2 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1906280000 definitions=main-1908300124 Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Fri, Aug 30, 2019 at 04:43:33PM +0800, Gao Xiang wrote: > Hi Dan, > > On Fri, Aug 30, 2019 at 11:34:45AM +0300, Dan Carpenter wrote: > > On Fri, Aug 30, 2019 at 12:04:41AM +0800, Gao Xiang wrote: > > > Anyway, I'm fine to delete them all if you like, but I think majority of these > > > are meaningful. > > > > > > data.c- /* page is already locked */ > > > data.c- DBG_BUGON(PageUptodate(page)); > > > data.c- > > > data.c: if (unlikely(err)) > > > data.c- SetPageError(page); > > > data.c- else > > > data.c- SetPageUptodate(page); > > > > If we cared about speed here then we would delete the DBG_BUGON() check > > because that's going to be expensive. The likely/unlikely annotations > > should be used in places a reasonable person thinks it will make a > > difference to benchmarks. > > DBG_BUGON will be a no-op ((void)x) in non-debugging mode, It expands to: ((void)PageUptodate(page)); Calling PageUptodate() doesn't do anything, but it isn't free. The time it takes to do that function call completely negates any speed up from using likely/unlikely. I'm really not trying to be a jerk... regards, dan carpenter