From mboxrd@z Thu Jan 1 00:00:00 1970 From: Fengguang Wu Subject: Re: [PATCH] mm: readahead: remove redundant ra_pages in file_ra_state Date: Fri, 26 Oct 2012 14:58:55 +0800 Message-ID: <20121026065855.GA9179@localhost> References: <20121024201921.GX4291@dastard> <20121025015014.GC29378@dastard> <50889FF1.9030107@gmail.com> <20121025025826.GB23462@localhost> <20121026002544.GI29378@dastard> <20121026012758.GA6282@localhost> <5089F5AD.5040708@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Dave Chinner , YingHang Zhu , akpm@linux-foundation.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org To: Ni zhan Chen Return-path: Content-Disposition: inline In-Reply-To: <5089F5AD.5040708@gmail.com> Sender: owner-linux-mm@kvack.org List-Id: linux-fsdevel.vger.kernel.org > static void shrink_readahead_size_eio(struct file *filp, > struct file_ra_state *ra) > { > - ra->ra_pages /= 4; > + spin_lock(&filp->f_lock); > + filp->f_mode |= FMODE_RANDOM; > + spin_unlock(&filp->f_lock); > > As the example in comment above this function, the read maybe still > sequential, and it will waste IO bandwith if modify to FMODE_RANDOM > directly. Yes immediately disabling readahead may hurt IO performance, the original '/ 4' may perform better when there are only 1-3 IO errors encountered. Thanks, Fengguang -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org