From mboxrd@z Thu Jan 1 00:00:00 1970 Message-Id: <200205151200.g4FC0MY13196@Port.imtp.ilyichevsk.odessa.ua> Content-Type: text/plain; charset="us-ascii" From: Denis Vlasenko Reply-To: vda@port.imtp.ilyichevsk.odessa.ua Subject: Re: [RFC][PATCH] iowait statistics Date: Wed, 15 May 2002 15:02:57 -0200 References: <3CE073FA.57DAC578@zip.com.au> In-Reply-To: <3CE073FA.57DAC578@zip.com.au> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: owner-linux-mm@kvack.org Return-Path: To: Andrew Morton , Rik van Riel Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org List-ID: On 14 May 2002 00:18, Andrew Morton wrote: > Rik van Riel wrote: > > 4) on SMP systems the iowait time can be overestimated, no big > > deal IMHO but cheap suggestions for improvement are welcome > > I suspect that a number of these statistical accounting mechanisms > are going to break. The new irq-affinity code works awfully well. > > The kernel profiler in 2.5 doesn't work very well at present. > When investigating this, I ran a busy-wait process. It attached > itself to CPU #3 and that CPU received precisely zero interrupts > across a five minute period. So the profiler cunningly avoids profiling > busy CPUs, which is rather counter-productive. Fortunate that oprofile > uses NMI. What, even local APIC interrupts did not happen on CPU#3 in these five mins? -- vda -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/