From owner-freebsd-current@FreeBSD.ORG Thu Feb 27 07:13:21 2014 Return-Path: Delivered-To: freebsd-current@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [8.8.178.115]) (using TLSv1 with cipher ADH-AES256-SHA (256/256 bits)) (No client certificate requested) by hub.freebsd.org (Postfix) with ESMTPS id DF61BA7 for ; Thu, 27 Feb 2014 07:13:21 +0000 (UTC) Received: from smtp.mei.co.jp (smtp.mei.co.jp [133.183.100.20]) by mx1.freebsd.org (Postfix) with ESMTP id 6546810F9 for ; Thu, 27 Feb 2014 07:13:21 +0000 (UTC) Received: from mail-gw.jp.panasonic.com ([157.8.1.157]) by smtp.mei.co.jp (8.12.11.20060614/3.7W/kc-maile12) with ESMTP id s1R7DJmV020283; Thu, 27 Feb 2014 16:13:19 +0900 (JST) Received: from epochmail.jp.panasonic.com ([157.8.1.130]) by mail.jp.panasonic.com (8.11.6p2/3.7W/kc-maili17) with ESMTP id s1R7DJ325660; Thu, 27 Feb 2014 16:13:19 +0900 Received: by epochmail.jp.panasonic.com (8.12.11.20060308/3.7W/lomi12) id s1R7DJ2j028441; Thu, 27 Feb 2014 16:13:19 +0900 Received: from localhost by lomi12.jp.panasonic.com (8.12.11.20060308/3.7W) with ESMTP id s1R7DIuX028413; Thu, 27 Feb 2014 16:13:18 +0900 Date: Thu, 27 Feb 2014 16:13:17 +0900 (JST) Message-Id: <20140227.161317.453723361596662298.okuno.kohji@jp.panasonic.com> To: jmg@funkthat.com Subject: Re: kqueue for usb_dev From: Kohji Okuno In-Reply-To: <20140227060232.GA47921@funkthat.com> References: <20140227.142615.924807465819500067.okuno.kohji@jp.panasonic.com> <20140227060232.GA47921@funkthat.com> Organization: Panasonic Corporation X-Mailer: Mew version 6.5 on Emacs 24.3 / Mule 6.0 (HANACHIRUSATO) Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Cc: freebsd-current@freebsd.org, okuno.kohji@jp.panasonic.com X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.17 Precedence: list List-Id: Discussions about the use of FreeBSD-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 27 Feb 2014 07:13:21 -0000 Hi John-Mark, Thank you for you comment. From: John-Mark Gurney > Kohji Okuno wrote this message on Thu, Feb 27, 2014 at 14:26 +0900: >> I tried add kqueue I/F to usb_dev.c. I attached my patch. >> What do you think about my patch? > > A few comments... > > 1) You should just drop the use of flag_iskevent and just > unconditionally call KNOTE... since you have the lock already held, > the cost is minimal (and w/ modern branch prediction, may be cheaper)... Should we set the use of flag_iskevent, when usb_filter_read() and usb_filter_write() return `0'? > 2) Why do you try to start read/write transfers in the _filter? You > should just check to see if data is available and not do work.. This > is also important since kqueue calls the filter just before delivering > the knote to userland to verify that there is still data, and it will > call your _event function for each knote on the fd... The work should > be started through other mechanisms, like read/write syscall or > interrupt or timeout/callout... If it's required to get results from > USB_IF_POLL, then it's fine.. I copied from usb_poll(). Should we try to start read/write transfers in usb_kqfilter()? Or should not we try to start read/write transfers in poll and kqueue? > 3) I don't see any calls to knlist_destroy... These calls are needed > to clean up the knlist... I understood. > Obviously the #if 1's will need to go... > > Also, I don't think your change is against HEAD.. The line numbers > in my version of usb_dev.c are different... I'm sorry. Many thanks, Kohji Okuno