From mboxrd@z Thu Jan 1 00:00:00 1970 From: James Bottomley Subject: Re: calling scsi_adjust_queue_depth() during I/O... Date: Fri, 05 Aug 2005 11:32:07 -0500 Message-ID: <1123259528.5003.36.camel@mulgrave> References: <20050804234155.GJ13374@plap.qlogic.org> <20050805075751.GN9369@suse.de> <20050805110911.GA22867@htj.dyndns.org> <42F350E6.2090109@gmail.com> <20050805123301.GA3311@htj.dyndns.org> Mime-Version: 1.0 Content-Type: text/plain Content-Transfer-Encoding: 7bit Return-path: Received: from stat16.steeleye.com ([209.192.50.48]:19407 "EHLO hancock.sc.steeleye.com") by vger.kernel.org with ESMTP id S263021AbVHEQce (ORCPT ); Fri, 5 Aug 2005 12:32:34 -0400 In-Reply-To: <20050805123301.GA3311@htj.dyndns.org> Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: Tejun Heo Cc: Jens Axboe , Andrew Vasquez , Linux-SCSI Mailing List On Fri, 2005-08-05 at 21:33 +0900, Tejun Heo wrote: > Here's the fix. It basically revives bqt->real_max_depth sans > allocation optimization in init_tag_map. I've also added a comment > explicitly noting that tag map cannot be shrunk to prevent other > morons like me. :-( Please try this one and let me know how it works. > If this is the correct fix, I'll repost properly to Jens and lkml with > detailed explanation on how it was broken in the original code and how > I broke it with my previous patch. Sorry. Actually, if you really want to adjust the array size downwards, there's a way we can do it: - If the bits that would be lost on shrinkage are all zero at the time blk_queue_resize_tags() is called, that means that there are no outstanding tags up there and the array can be shrunk immediately. - If there are outstanding tags between the new and the old depth, the array can be shrunk when the last one of these returns, say in blk_rq_end_tag() James