Re: Performance regressions in "boot_time" tests in Linux 5.8 Kernel

[Mike Rapoport]

Hi Rahul,

On Tue, Nov 24, 2020 at 03:03:40PM +0000, Rahul Gopakumar wrote:
> Hi Baoquan,
> 
> We applied the new patch to 5.10 rc3 and tested it. We are still
> observing the same page corruption issue which we saw with the
> old patch. This is causing 3 secs delay in boot time.
> 
> Attached dmesg log from the new patch and also from vanilla
> 5.10 rc3 kernel.
> 
> There are multiple lines like below in the dmesg log of the
> new patch.
> 
> "BUG: Bad page state in process swapper  pfn:ab08001"

Can you please run your test with the below patch and send output of

	dmesg | grep defer


diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index eaa227a479e4..ce7ec660c777 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -455,6 +455,7 @@ defer_init(int nid, unsigned long pfn, unsigned long end_pfn)
 	nr_initialised++;
 	if ((nr_initialised > PAGES_PER_SECTION) &&
 	    (pfn & (PAGES_PER_SECTION - 1)) == 0) {
+		pr_info("=> %s: nid: %d pfn: %lx\n", __func__, nid, pfn);
 		NODE_DATA(nid)->first_deferred_pfn = pfn;
 		return true;
 	}

> ________________________________________
> From: bhe@xxxxxxxxxx <bhe@xxxxxxxxxx>
> Sent: 22 November 2020 6:38 AM
> To: Rahul Gopakumar
> Cc: linux-mm@xxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; akpm@xxxxxxxxxxxxxxxxxxxx; natechancellor@xxxxxxxxx; ndesaulniers@xxxxxxxxxx; clang-built-linux@xxxxxxxxxxxxxxxx; rostedt@xxxxxxxxxxx; Rajender M; Yiu Cho Lau; Peter Jonasson; Venkatesh Rajaram
> Subject: Re: Performance regressions in "boot_time" tests in Linux 5.8 Kernel
> 
> On 11/20/20 at 03:11am, Rahul Gopakumar wrote:
> > Hi Baoquan,
> >
> > To which commit should we apply the draft patch. We tried applying
> > the patch to the commit 3e4fb4346c781068610d03c12b16c0cfb0fd24a3
> > (the one we used for applying the previous patch) but it fails.
> 
> I tested on 5.10-rc3+. You can append below change to the old patch in
> your testing kernel.
> 
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index fa6076e1a840..5e5b74e88d69 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -448,6 +448,8 @@ defer_init(int nid, unsigned long pfn, unsigned long end_pfn)
>         if (end_pfn < pgdat_end_pfn(NODE_DATA(nid)))
>                 return false;
> 
> +       if (NODE_DATA(nid)->first_deferred_pfn != ULONG_MAX)
> +               return true;
>         /*
>          * We start only with one section of pages, more pages are added as
>          * needed until the rest of deferred pages are initialized.
> 




-- 
Sincerely yours,
Mike.