From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from e19.ny.us.ibm.com (e19.ny.us.ibm.com [129.33.205.209]) (using TLSv1.2 with cipher CAMELLIA256-SHA (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 5DD281A0007 for ; Thu, 25 Feb 2016 15:52:44 +1100 (AEDT) Received: from localhost by e19.ny.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Wed, 24 Feb 2016 23:52:41 -0500 Received: from b01cxnp22035.gho.pok.ibm.com (b01cxnp22035.gho.pok.ibm.com [9.57.198.25]) by d01dlp03.pok.ibm.com (Postfix) with ESMTP id E6BC0C90042 for ; Wed, 24 Feb 2016 23:52:35 -0500 (EST) Received: from d01av04.pok.ibm.com (d01av04.pok.ibm.com [9.56.224.64]) by b01cxnp22035.gho.pok.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id u1P4qcQd32571618 for ; Thu, 25 Feb 2016 04:52:38 GMT Received: from d01av04.pok.ibm.com (localhost [127.0.0.1]) by d01av04.pok.ibm.com (8.14.4/8.14.4/NCO v10.0 AVout) with ESMTP id u1P4qced018088 for ; Wed, 24 Feb 2016 23:52:38 -0500 From: "Aneesh Kumar K.V" To: Hugh Dickins Cc: Paul Mackerras , linuxppc-dev@lists.ozlabs.org, linux-mm@kvack.org Subject: Re: Problems with swapping in v4.5-rc on POWER In-Reply-To: References: Date: Thu, 25 Feb 2016 10:22:34 +0530 Message-ID: <877fhttmr1.fsf@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Hugh Dickins writes: > I've plagiarized the subject from Paulus's "Problems with THP" mail > last weekend; but my similar problems are on PowerMac G5 baremetal, > with 4kB pages, not capable of THP and no THP configured in. > > Under heavily swapping load, running kernel builds on tmpfs in limited > memory, I've been seeing random segfaults too, internal compiler errors > etc. Not easily reproduced: sometimes happens in minutes, sometimes > not for several hours. > > I tried and failed to construct a reproducer for you: my lack of a good > recipe has deterred me from reporting it, and seeing Paulus's mail on > THP gave me hope that the answer would come up in that thread; but no, > that was quickly resolved as a THP issue, since fixed. > > (Mine had appeared to be fixed in v4.5-rc4 anyway; but I guess I > just didn't try hard enough, it resurfaced on -rc5 immediately.) > > I've seen no sign of such problems on x86. And I saw no sign of such > problems on v4.4-rc8-mm1, when I included the fixes to the _PAGE_PTE > and _PAGE_SWP_SOFT_DIRTY swapoff issues we discussed back then (in > 33 hours of load, should be good enough; but did see such problems > a couple of times before including those fixes - I took them to be > a side-effect of the page flags issue, but now rather doubt that). > Can you test the impact of the merge listed below ?(ie, revert the merge and see if we can reproduce and also verify with merge applied). This will give us a set of commits to look closer. We had quiet a lot of page table related changes going in this merge window. f689b742f217b2ffe7 ("Pull powerpc updates from Michael Ellerman:") That is the merge commit that added _PAGE_PTE. > The minutes or hours thing: I wonder if that indicates a missing > initialization somewhere: that can easily show up soon after booting, > but then the machine settles into a steady state of reusing the same > structures, now initialized; until much later something disturbs the > state and it has to allocate more. Sheer speculation, but I wonder. > -aneesh