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mm: compaction: skip memory hole rapidly when isolating migratable pages 

On some machines, the normal zone can have a large memory hole like below
memory layout, and we can see the range from 0x100000000 to 0x1800000000
is a hole.  So when isolating some migratable pages, the scanner can meet
the hole and it will take more time to skip the large hole.  From my
measurement, I can see the isolation scanner will take 80us ~ 100us to
skip the large hole [0x100000000 - 0x1800000000].

So adding a new helper to fast search next online memory section to skip
the large hole can help to find next suitable pageblock efficiently.  With
this patch, I can see the large hole scanning only takes < 1us.

[    0.000000] Zone ranges:
[    0.000000]   DMA      [mem 0x0000000040000000-0x00000000ffffffff]
[    0.000000]   DMA32    empty
[    0.000000]   Normal   [mem 0x0000000100000000-0x0000001fa7ffffff]
[    0.000000] Movable zone start for each node
[    0.000000] Early memory node ranges
[    0.000000]   node   0: [mem 0x0000000040000000-0x0000000fffffffff]
[    0.000000]   node   0: [mem 0x0000001800000000-0x0000001fa3c7ffff]
[    0.000000]   node   0: [mem 0x0000001fa3c80000-0x0000001fa3ffffff]
[    0.000000]   node   0: [mem 0x0000001fa4000000-0x0000001fa402ffff]
[    0.000000]   node   0: [mem 0x0000001fa4030000-0x0000001fa40effff]
[    0.000000]   node   0: [mem 0x0000001fa40f0000-0x0000001fa73cffff]
[    0.000000]   node   0: [mem 0x0000001fa73d0000-0x0000001fa745ffff]
[    0.000000]   node   0: [mem 0x0000001fa7460000-0x0000001fa746ffff]
[    0.000000]   node   0: [mem 0x0000001fa7470000-0x0000001fa758ffff]
[    0.000000]   node   0: [mem 0x0000001fa7590000-0x0000001fa7ffffff]

[baolin.wang@linux.alibaba.com: limit next_ptn to not exceed cc->free_pfn]
  Link: https://lkml.kernel.org/r/a1d859c28af0c7e85e91795e7473f553eb180a9d.1686813379.git.baolin.wang@linux.alibaba.com
Link: https://lkml.kernel.org/r/75b4c8ca36bf44ad8c42bf0685ac19d272e426ec.1686705221.git.baolin.wang@linux.alibaba.com
Signed-off-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Suggested-by: David Hildenbrand <david@redhat.com>
Acked-by: David Hildenbrand <david@redhat.com>
Acked-by: "Huang, Ying" <ying.huang@intel.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Baolin Wang 2023-06-14 16:40:20 +08:00 committed by Andrew Morton
parent 8c293a6353
commit 9721fd8235
1 changed files with 34 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

35
mm/compaction.c
View File

@ -229,6 +229,33 @@ static void reset_cached_positions(struct zone *zone)
pageblock_start_pfn(zone_end_pfn(zone) - 1);
}
#ifdef CONFIG_SPARSEMEM
/*
* If the PFN falls into an offline section, return the start PFN of the
* next online section. If the PFN falls into an online section or if
* there is no next online section, return 0.
*/
static unsigned long skip_offline_sections(unsigned long start_pfn)
{
unsigned long start_nr = pfn_to_section_nr(start_pfn);
if (online_section_nr(start_nr))
return 0;
while (++start_nr <= __highest_present_section_nr) {
if (online_section_nr(start_nr))
return section_nr_to_pfn(start_nr);
}
return 0;
}
#else
static unsigned long skip_offline_sections(unsigned long start_pfn)
{
return 0;
}
#endif
/*
* Compound pages of >= pageblock_order should consistently be skipped until
* released. It is always pointless to compact pages of such order (if they are
@ -1955,8 +1982,14 @@ static isolate_migrate_t isolate_migratepages(struct compact_control *cc)
page = pageblock_pfn_to_page(block_start_pfn,
block_end_pfn, cc->zone);
if (!page)
if (!page) {
unsigned long next_pfn;
next_pfn = skip_offline_sections(block_start_pfn);
if (next_pfn)
block_end_pfn = min(next_pfn, cc->free_pfn);
continue;
}
/*
* If isolation recently failed, do not retry. Only check the