From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pg0-f71.google.com (mail-pg0-f71.google.com [74.125.83.71]) by kanga.kvack.org (Postfix) with ESMTP id 8B7906B0253 for ; Thu, 28 Dec 2017 12:41:51 -0500 (EST) Received: by mail-pg0-f71.google.com with SMTP id i2so6060039pgq.8 for ; Thu, 28 Dec 2017 09:41:51 -0800 (PST) Received: from bedivere.hansenpartnership.com (bedivere.hansenpartnership.com. [66.63.167.143]) by mx.google.com with ESMTPS id c18si24900140plz.125.2017.12.28.09.41.50 for (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Thu, 28 Dec 2017 09:41:50 -0800 (PST) Message-ID: <1514482907.3040.15.camel@HansenPartnership.com> Subject: Re: Hang with v4.15-rc trying to swap back in From: James Bottomley Date: Thu, 28 Dec 2017 09:41:47 -0800 In-Reply-To: <20171227235643.GA10532@bbox> References: <1514398340.3986.10.camel@HansenPartnership.com> <1514407817.4169.4.camel@HansenPartnership.com> <20171227232650.GA9702@bbox> <1514417689.3083.1.camel@HansenPartnership.com> <20171227235643.GA10532@bbox> Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: owner-linux-mm@kvack.org List-ID: To: Minchan Kim Cc: Linux Memory Management List , Andrew Morton , Thorsten Leemhuis On Thu, 2017-12-28 at 08:56 +0900, Minchan Kim wrote: > On Wed, Dec 27, 2017 at 03:34:49PM -0800, James Bottomley wrote: > > > > On Thu, 2017-12-28 at 08:26 +0900, Minchan Kim wrote: > > > > > > Hello James, > > > > > > On Wed, Dec 27, 2017 at 12:50:17PM -0800, James Bottomley wrote: > > > > > > > > > > > > Reverting these three patches fixes the problem: > > > > > > > > commit aa8d22a11da933dbf880b4933b58931f4aefe91c > > > > Author: Minchan Kim > > > > Date:A A A Wed Nov 15 17:33:11 2017 -0800 > > > > > > > > A A A A mm: swap: SWP_SYNCHRONOUS_IO: skip swapcache only if > > > > swapped page has no other reference > > > > > > > > commit 0bcac06f27d7528591c27ac2b093ccd71c5d0168 > > > > Author: Minchan Kim > > > > Date:A A A Wed Nov 15 17:33:07 2017 -0800 > > > > > > > > A A A A mm, swap: skip swapcache for swapin of synchronous device > > > > > > > > Also need to revert: > > > > > > > > commit e9a6effa500526e2a19d5ad042cb758b55b1ef93 > > > > Author: Huang Ying > > > > Date:A A A Wed Nov 15 17:33:15 2017 -0800 > > > > > > > > A A A A mm, swap: fix false error message in __swp_swapcount() > > > > > > > > (The latter is simply because it used a function that is > > > > eliminated by one of the other reversions). A They came into the > > > > merge window via the -mm tree as part of a 4 part series: > > > > > > > > Subject: [PATCH v2 0/4] skip swapcache for super fast > > > > device > > > > Message-Id: <1505886205-9671-1-git-send-email- > > > > minchan@kernel.org > > > > > > > > > > > > > > > > > > > > > > > James > > > > > > Thanks for the report. > > > Patches are related to synchronous swap devices like brd, zram, > > > nvdimm so > > > > > > 1. What swap device do you use among them? > > > > I've reproduced on nvme and sata spinning rust. > > > > > > > > 2. Could you tell me how you can reproduce it? > > > > The way to reproduce is to force something to swap and then get it > > to try to touch the page again. A I do this on my systems by using a > > large virtual machine, as I said in the email. A There isn't really > > any definitive reproduction method beyond that. > > > > Thanks for the information. It seems I made a bug on do_swap_page. I > want to confirm before sending formal patch. Could you try on it? > > diff --git a/mm/memory.c b/mm/memory.c > index ca5674cbaff2..240521f1322d 100644 > --- a/mm/memory.c > +++ b/mm/memory.c > @@ -2889,9 +2889,12 @@ int do_swap_page(struct vm_fault *vmf) > A > A > A delayacct_set_flag(DELAYACCT_PF_SWAPIN); > - if (!page) > + if (!page) { > A page = lookup_swap_cache(entry, vma_readahead ? vma > : NULL, > A A vmf->address); > + swapcache = page; > + } > + This hangs in precisely the same way first kworker then kswapd with the same stack trace. I'd guess that since they're both in io_schedule, the problem is that the io_scheduler is taking far too long servicing the requests due to some priority issue you've introduced. Since we're at -rc5, soon to be -rc6, let's just revert the whole series and you can retry it for 4.16. A The whole point seems to be for zram, which isn't really a huge use case. James -- 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/ . Don't email: email@kvack.org