Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751611AbWE0Pzo (ORCPT ); Sat, 27 May 2006 11:55:44 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751601AbWE0PwW (ORCPT ); Sat, 27 May 2006 11:52:22 -0400 Received: from smtp.ustc.edu.cn ([202.38.64.16]:221 "HELO ustc.edu.cn") by vger.kernel.org with SMTP id S1751605AbWE0Pvj (ORCPT ); Sat, 27 May 2006 11:51:39 -0400 Message-ID: <348745096.16246@ustc.edu.cn> X-EYOUMAIL-SMTPAUTH: wfg@mail.ustc.edu.cn Message-Id: <20060527155137.552915509@localhost.localdomain> References: <20060527154849.927021763@localhost.localdomain> Date: Sat, 27 May 2006 23:49:13 +0800 From: Wu Fengguang To: Andrew Morton Cc: linux-kernel@vger.kernel.org, Wu Fengguang Subject: [PATCH 24/32] readahead: thrashing recovery method Content-Disposition: inline; filename=readahead-method-onthrash.patch Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1980 Lines: 68 Readahead policy after thrashing. It tries to recover gracefully from the thrashing. Signed-off-by: Wu Fengguang --- mm/readahead.c | 42 ++++++++++++++++++++++++++++++++++++++++++ 1 files changed, 42 insertions(+) --- linux-2.6.17-rc4-mm3.orig/mm/readahead.c +++ linux-2.6.17-rc4-mm3/mm/readahead.c @@ -1619,6 +1619,48 @@ try_readahead_on_seek(struct file_ra_sta } /* + * Readahead thrashing recovery. + */ +static unsigned long +thrashing_recovery_readahead(struct address_space *mapping, + struct file *filp, struct file_ra_state *ra, + pgoff_t index, unsigned long ra_max) +{ + unsigned long ra_size; + + if (probe_page(mapping, index - 1)) + ra_account(ra, RA_EVENT_READAHEAD_MUTILATE, + ra->readahead_index - index); + ra_account(ra, RA_EVENT_READAHEAD_THRASHING, + ra->readahead_index - index); + + /* + * Some thrashing occur in (ra_index, la_index], in which case the + * old read-ahead chunk is lost soon after the new one is allocated. + * Ensure that we recover all needed pages in the old chunk. + */ + if (index < ra->ra_index) + ra_size = ra->ra_index - index; + else { + /* After thrashing, we know the exact thrashing-threshold. */ + ra_size = ra->hit0; + update_ra_thrash_bytes(mapping->backing_dev_info, ra_size); + + /* And we'd better be a bit conservative. */ + ra_size = ra_size * 3 / 4; + } + + if (ra_size > ra_max) + ra_size = ra_max; + + ra_set_class(ra, RA_CLASS_THRASHING); + ra_set_index(ra, index, index); + ra_set_size(ra, ra_size, ra_size / LOOKAHEAD_RATIO); + + return ra_dispatch(ra, mapping, filp); +} + +/* * ra_min is mainly determined by the size of cache memory. Reasonable? * * Table of concrete numbers for 4KB page size: -- - 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/