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 <minchan@xxxxxxxxxx>
> > > > Date: Wed Nov 15 17:33:11 2017 -0800
> > > >
> > > > mm: swap: SWP_SYNCHRONOUS_IO: skip swapcache only if
> > > > swapped page has no other reference
> > > >
> > > > commit 0bcac06f27d7528591c27ac2b093ccd71c5d0168
> > > > Author: Minchan Kim <minchan@xxxxxxxxxx>
> > > > Date: Wed Nov 15 17:33:07 2017 -0800
> > > >
> > > > mm, swap: skip swapcache for swapin of synchronous device
> > > >
> > > > Also need to revert:
> > > >
> > > > commit e9a6effa500526e2a19d5ad042cb758b55b1ef93
> > > > Author: Huang Ying <huang.ying.caritas@xxxxxxxxx>
> > > > Date: Wed Nov 15 17:33:15 2017 -0800
> > > >
> > > > 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). 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@xxxxxxxxxx
> > > > >
> > > > >
> > > > >
> > > >
> > > > 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. I do this on my systems by using a
> > large virtual machine, as I said in the email. 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)
>
>
> delayacct_set_flag(DELAYACCT_PF_SWAPIN);
> - if (!page)
> + if (!page) {
> page = lookup_swap_cache(entry, vma_readahead ? vma
> : NULL,
> 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. 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@xxxxxxxxx. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
