From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Mallick, Asit K" Date: Fri, 14 Mar 2003 20:26:49 +0000 Subject: RE: [Linux-ia64] Single bundle loops on Itanium-2 sometimes run slow Message-Id: List-Id: References: In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: linux-ia64@vger.kernel.org Jack, We are looking at this. I am assuming that if the bundle is aligned then you do not see this problem. Is my assumption correct? Thanks, Asit > -----Original Message----- > From: David Mosberger [mailto:davidm@napali.hpl.hp.com] > Sent: Friday, March 14, 2003 11:47 AM > To: Jack Steiner > Cc: linux-ia64@linuxia64.org > Subject: Re: [Linux-ia64] Single bundle loops on Itanium-2 sometimes run > slow > > >>>>> On Fri, 14 Mar 2003 12:51:43 -0600 (CST), Jack Steiner > said: > > Jack> SUMMARY: It appears that if a single bundle misaligned loop is > Jack> interrupted (timer, etc), when the loop is resumed, it > Jack> sometimes runs at about 1/3 the normal rate until the loop > Jack> completes. (I dont mean 1 or a few iterations of the loop!!) > > Jack> 4000000000000eb0: [MIB] adds r8=1,r32 > Jack> 4000000000000eb6: adds r32=-1,r32 4000000000000ebc: > Jack> br.cloop.sptk.few 4000000000000eb0 ;; > > > Jack> If "noise" is present, pfmon shows significant lost cycles due > Jack> to BE_LOST_BW_DUE_TO_FE_BR_ILOCK. A 15 second sample shows: > Jack> BE_LOST_BW_DUE_TO_FE_BR_ILOCK = 423 for good run > Jack> BE_LOST_BW_DUE_TO_FE_BR_ILOCK = 105935651 for noisy run > > Jack> Changing the test so that code is at different addresses > Jack> effects the likelyhood that noise will occur. Sometimes noise > Jack> occurs on only a subset of the cpus. Sometimes booting a > Jack> different kernel changes the likelyhood of seeing noise. > > Jack> Has anyone seen this behavior or have an explanation. > > Can you check whether the problem goes away when you turn the loop > into a 2-cycle loop? My bet is that it will. > > --david > > _______________________________________________ > Linux-IA64 mailing list > Linux-IA64@linuxia64.org > http://lists.linuxia64.org/lists/listinfo/linux-ia64