Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932927Ab3ECONv (ORCPT ); Fri, 3 May 2013 10:13:51 -0400 Received: from fallback7.mail.ru ([94.100.176.135]:35282 "EHLO fallback7.mail.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932690Ab3ECONu (ORCPT ); Fri, 3 May 2013 10:13:50 -0400 X-Greylist: delayed 470 seconds by postgrey-1.27 at vger.kernel.org; Fri, 03 May 2013 10:13:50 EDT Message-ID: <5183D196.2080305@list.ru> Date: Fri, 03 May 2013 19:02:46 +0400 From: Stas Sergeev User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130311 Thunderbird/17.0.4 MIME-Version: 1.0 To: Jarkko Huijts CC: Alan Cox , Linux kernel , Caylan Van Larson , "Rafael J. Wysocki" Subject: Regression: ftdi_sio is slow (since Wed Oct 10 15:05:06 2012) Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Spam: Not detected X-Mras: Ok Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 926 Lines: 24 Hi. We have a regression because of this patch: http://lkml.indiana.edu/hypermail/linux/kernel/1210.1/01456.html While it is arguably reasonable to have this for tcdrain or close, it also slows down poll/select a lot because n_tty_poll() does this: tty_chars_in_buffer(tty) < WAKEUP_CHARS And it also slows down TIOCOUTQ ioctl I think (not measured). The slowdown of select() is big, the customer reports the inability to work that way. Is this patch really needed? I mean, if the time to check TEMT is longer than to xmit that char, then what's the use? Or, if it is really a big deal, I guess it would be necessary to add a separate, .chars_in_buffer_fast method. Thoughts? -- 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/