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Message-ID: <20151208051439.GA20797@aaronlu.sh.intel.com>
Date: Tue, 8 Dec 2015 13:14:39 +0800
From: Aaron Lu <aaron.lu@...el.com>
To: Joonsoo Kim <iamjoonsoo.kim@....com>
Cc: Vlastimil Babka <vbabka@...e.cz>, linux-mm@...ck.org,
linux-kernel@...r.kernel.org, Rik van Riel <riel@...hat.com>,
David Rientjes <rientjes@...gle.com>,
Mel Gorman <mgorman@...e.de>, Minchan Kim <minchan@...nel.org>
Subject: Re: [RFC 0/3] reduce latency of direct async compaction
On Tue, Dec 08, 2015 at 09:41:18AM +0900, Joonsoo Kim wrote:
> On Mon, Dec 07, 2015 at 04:59:56PM +0800, Aaron Lu wrote:
> > On Mon, Dec 07, 2015 at 04:35:24PM +0900, Joonsoo Kim wrote:
> > > It looks like overhead still remain. I guess that migration scanner
> > > would call pageblock_pfn_to_page() for more extended range so
> > > overhead still remain.
> > >
> > > I have an idea to solve his problem. Aaron, could you test following patch
> > > on top of base? It tries to skip calling pageblock_pfn_to_page()
> >
> > It doesn't apply on top of 25364a9e54fb8296837061bf684b76d20eec01fb
> > cleanly, so I made some changes to make it apply and the result is:
> > https://github.com/aaronlu/linux/commit/cb8d05829190b806ad3948ff9b9e08c8ba1daf63
>
> Yes, that's okay. I made it on my working branch but it will not result in
> any problem except applying.
>
> >
> > There is a problem occured right after the test starts:
> > [ 58.080962] BUG: unable to handle kernel paging request at ffffea0082000018
> > [ 58.089124] IP: [<ffffffff81193f29>] compaction_alloc+0xf9/0x270
> > [ 58.096109] PGD 107ffd6067 PUD 207f7d5067 PMD 0
> > [ 58.101569] Oops: 0000 [#1] SMP
>
> I did some mistake. Please test following patch. It is also made
> on my working branch so you need to resolve conflict but it would be
> trivial.
>
> I inserted some logs to check whether zone is contiguous or not.
> Please check that normal zone is set to contiguous after testing.
Yes it is contiguous, but unfortunately, the problem remains:
[ 56.536930] check_zone_contiguous: Normal
[ 56.543467] check_zone_contiguous: Normal: contiguous
[ 56.549640] BUG: unable to handle kernel paging request at ffffea0082000018
[ 56.557717] IP: [<ffffffff81193f29>] compaction_alloc+0xf9/0x270
[ 56.564719] PGD 107ffd6067 PUD 207f7d5067 PMD 0
Full dmesg attached.
Thanks,
Aaron
>
> Thanks.
>
> ------>8------
> From 4a1a08d8ab3fb165b87ad2ec0a2000ff6892330f Mon Sep 17 00:00:00 2001
> From: Joonsoo Kim <iamjoonsoo.kim@....com>
> Date: Mon, 7 Dec 2015 14:51:42 +0900
> Subject: [PATCH] mm/compaction: Optimize pageblock_pfn_to_page() for
> contiguous zone
>
> Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@....com>
> ---
> include/linux/mmzone.h | 1 +
> mm/compaction.c | 54 +++++++++++++++++++++++++++++++++++++++++++++++++-
> 2 files changed, 54 insertions(+), 1 deletion(-)
>
> diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
> index e23a9e7..573f9a9 100644
> --- a/include/linux/mmzone.h
> +++ b/include/linux/mmzone.h
> @@ -521,6 +521,7 @@ struct zone {
> #endif
>
> #if defined CONFIG_COMPACTION || defined CONFIG_CMA
> + int contiguous;
> /* Set to true when the PG_migrate_skip bits should be cleared */
> bool compact_blockskip_flush;
> #endif
> diff --git a/mm/compaction.c b/mm/compaction.c
> index 67b8d90..cb5c7a2 100644
> --- a/mm/compaction.c
> +++ b/mm/compaction.c
> @@ -88,7 +88,7 @@ static inline bool migrate_async_suitable(int migratetype)
> * the first and last page of a pageblock and avoid checking each individual
> * page in a pageblock.
> */
> -static struct page *pageblock_pfn_to_page(unsigned long start_pfn,
> +static struct page *__pageblock_pfn_to_page(unsigned long start_pfn,
> unsigned long end_pfn, struct zone *zone)
> {
> struct page *start_page;
> @@ -114,6 +114,56 @@ static struct page *pageblock_pfn_to_page(unsigned long start_pfn,
> return start_page;
> }
>
> +static inline struct page *pageblock_pfn_to_page(unsigned long start_pfn,
> + unsigned long end_pfn, struct zone *zone)
> +{
> + if (zone->contiguous == 1)
> + return pfn_to_page(start_pfn);
> +
> + return __pageblock_pfn_to_page(start_pfn, end_pfn, zone);
> +}
> +
> +static void check_zone_contiguous(struct zone *zone)
> +{
> + unsigned long block_start_pfn = zone->zone_start_pfn;
> + unsigned long block_end_pfn;
> + unsigned long pfn;
> +
> + /* Already checked */
> + if (zone->contiguous)
> + return;
> +
> + printk("%s: %s\n", __func__, zone->name);
> + block_end_pfn = ALIGN(block_start_pfn + 1, pageblock_nr_pages);
> + for (; block_start_pfn < zone_end_pfn(zone);
> + block_start_pfn = block_end_pfn,
> + block_end_pfn += pageblock_nr_pages) {
> +
> + block_end_pfn = min(block_end_pfn, zone_end_pfn(zone));
> +
> + if (!__pageblock_pfn_to_page(block_start_pfn,
> + block_end_pfn, zone)) {
> + /* We have hole */
> + zone->contiguous = -1;
> + printk("%s: %s: uncontiguous\n", __func__, zone->name);
> + return;
> + }
> +
> + /* Check validity of pfn within pageblock */
> + for (pfn = block_start_pfn; pfn < block_end_pfn; pfn++) {
> + if (!pfn_valid_within(pfn)) {
> + zone->contiguous = -1;
> + printk("%s: %s: uncontiguous\n", __func__, zone->name);
> + return;
> + }
> + }
> + }
> +
> + /* We don't have hole */
> + zone->contiguous = 1;
> + printk("%s: %s: contiguous\n", __func__, zone->name);
> +}
> +
> #ifdef CONFIG_COMPACTION
>
> /* Do not skip compaction more than 64 times */
> @@ -1353,6 +1403,8 @@ static int compact_zone(struct zone *zone, struct compact_control *cc)
> ;
> }
>
> + check_zone_contiguous(zone);
> +
> /*
> * Clear pageblock skip if there were failures recently and compaction
> * is about to be retried after being deferred. kswapd does not do
> --
> 1.9.1
>
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