From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ivo Sieben Subject: Re: Deterministic behavior for TTY serial Date: Thu, 3 May 2012 17:28:47 +0200 Message-ID: References: <20120419001407.GA24710@kroah.com> <20120419154609.GA9263@kroah.com> <20120501160456.3b0b5e34@pyramind.ukuu.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Return-path: In-Reply-To: Sender: linux-rt-users-owner@vger.kernel.org To: Greg KH , linux-serial@vger.kernel.org, Alan Cox , RT List-Id: linux-serial@vger.kernel.org Hi, > > The PREEMPT_RT uses mutexes for "normal" spin locks that do not > disable interrupts... > I'll try to use raw spinlocks in this code section and for the tty flip buffer > See if that can solve my problem. > > If you have other ideas... let me know! > > Regards, > Ivo I've changed some small things to the tty layer (see my other 3 RFC patches I've send). Performance increased with my loopback stress test: - Old situation: average read call last for 50us, with peaks up to 230 us - New situation: average read call still 50us, peak up to 60 us - Write was stable in both situations: average of 90 us, peak up to 100 us Only the very first read & write took extra time (128 us for read, 143 for write) I'm still investigating that... Feedback is very appreciated. Regards, Ivo Sieben