On Tue, Dec 08, 2015 at 01:14:39PM +0800, Aaron Lu wrote: > 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 > Maybe, I find the reason. cc->free_pfn can be initialized to invalid pfn that isn't checked so optimized pageblock_pfn_to_page() causes BUG(). I add work-around for this problem at isolate_freepages(). Please test following one. Thanks. ---------->8--------------- >From 7e954a68fb555a868acc5860627a1ad8dadbe3bf Mon Sep 17 00:00:00 2001 From: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx> 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@xxxxxxx> --- include/linux/mmzone.h | 1 + mm/compaction.c | 60 +++++++++++++++++++++++++++++++++++++++++++++++++- 2 files changed, 60 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 de3e1e7..ff5fb04 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 */ @@ -948,6 +998,12 @@ static void isolate_freepages(struct compact_control *cc) unsigned long low_pfn; /* lowest pfn scanner is able to scan */ struct list_head *freelist = &cc->freepages; + /* Work-around */ + if (zone->contiguous == 1 && + cc->free_pfn == zone_end_pfn(zone) && + cc->free_pfn == cc->free_pfn & ~(pageblock_nr_pages-1)) + cc->free_pfn -= pageblock_nr_pages; + /* * Initialise the free scanner. The starting point is where we last * successfully isolated from, zone-cached value, or the end of the @@ -1356,6 +1412,8 @@ 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 -- 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>