From mboxrd@z Thu Jan 1 00:00:00 1970 From: Vadim Lobanov Subject: Re: [RFC][PATCH] irq: remove IRQF_DISABLED Date: Mon, 2 Mar 2009 10:45:20 -0800 Message-ID: <200903021045.20723.vlobanov@speakeasy.net> References: <1235996477.5330.174.camel@laptop> Mime-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org To: Linus Torvalds Cc: Peter Zijlstra , Ingo Molnar , Thomas Gleixner , lkml , linux-arch , Andrew Morton List-Id: linux-arch.vger.kernel.org On Monday 02 March 2009 09:11:54 Linus Torvalds wrote: > The thing is, with PIO, a 512-byte disk read ends up doing 256 16-bit word > reads from the controller, each potentially up to 600ns long (PIO0 > timings). That's 150ms - for a single sector! Out of curiosity, the peanut gallery wishes to ask: Is the above supposed to be 600us (*1000), or 150us (/1000)? Probably the latter. > For example, Mode2 timings are probably still something we should consider > realistic, and that's 240ns per word - a single sector now takes ~60ms to > read off the disk. Same factor of 1000 question here. > And we don't do single sectors. Most transfers will be 8 sectors (4k > contiguos read). So now that 60ms is 480ms per such IDE interrupt. And > even with the _good_ timings, we're certainly looking at a reduction of > that to about half. > > Imagine what happens when we have interrupts disabled for half a second at > a time. -- Vadim Lobanov From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.impinj.com ([206.169.229.170]:47182 "EHLO earth.impinj.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751577AbZCBSwX (ORCPT ); Mon, 2 Mar 2009 13:52:23 -0500 From: Vadim Lobanov Subject: Re: [RFC][PATCH] irq: remove IRQF_DISABLED Date: Mon, 2 Mar 2009 10:45:20 -0800 References: <1235996477.5330.174.camel@laptop> In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-ID: <200903021045.20723.vlobanov@speakeasy.net> Sender: linux-arch-owner@vger.kernel.org List-ID: To: Linus Torvalds Cc: Peter Zijlstra , Ingo Molnar , Thomas Gleixner , lkml , linux-arch , Andrew Morton Message-ID: <20090302184520.LIfVZOPxxjIzBj5DYoMFIriX68RQgIu-YDpl7T7he60@z> On Monday 02 March 2009 09:11:54 Linus Torvalds wrote: > The thing is, with PIO, a 512-byte disk read ends up doing 256 16-bit word > reads from the controller, each potentially up to 600ns long (PIO0 > timings). That's 150ms - for a single sector! Out of curiosity, the peanut gallery wishes to ask: Is the above supposed to be 600us (*1000), or 150us (/1000)? Probably the latter. > For example, Mode2 timings are probably still something we should consider > realistic, and that's 240ns per word - a single sector now takes ~60ms to > read off the disk. Same factor of 1000 question here. > And we don't do single sectors. Most transfers will be 8 sectors (4k > contiguos read). So now that 60ms is 480ms per such IDE interrupt. And > even with the _good_ timings, we're certainly looking at a reduction of > that to about half. > > Imagine what happens when we have interrupts disabled for half a second at > a time. -- Vadim Lobanov