From: Hui Zhu <zhuhui@xxxxxxxxxx> Subject: zsmalloc: zs_page_migrate: skip unnecessary loops but not return -EBUSY if zspage is not inuse Getting -EBUSY from zs_page_migrate will make migration slow (retry) or fail (zs_page_putback will schedule_work free_work, but it cannot ensure the success). I noticed this issue because my Kernel patched (https://lkml.org/lkml/2014/5/28/113) that will remove retry in __alloc_contig_migrate_range. This retry willhandle the -EBUSY because it will re-isolate the page and re-call migrate_pages. Without it will make cma_alloc fail at once with -EBUSY. According to the review from Minchan Kim in https://lkml.org/lkml/2014/5/28/113, I update the patch to skip unnecessary loops but not return -EBUSY if zspage is not inuse. Following is what I got with highalloc-performance in a vbox with 2 cpu 1G memory 512 zram as swap. And the swappiness is set to 100. ori ne orig new Minor Faults 50805113 50830235 Major Faults 43918 56530 Swap Ins 42087 55680 Swap Outs 89718 104700 Allocation stalls 0 0 DMA allocs 57787 52364 DMA32 allocs 47964599 48043563 Normal allocs 0 0 Movable allocs 0 0 Direct pages scanned 45493 23167 Kswapd pages scanned 1565222 1725078 Kswapd pages reclaimed 1342222 1503037 Direct pages reclaimed 45615 25186 Kswapd efficiency 85% 87% Kswapd velocity 1897.101 1949.042 Direct efficiency 100% 108% Direct velocity 55.139 26.175 Percentage direct scans 2% 1% Zone normal velocity 1952.240 1975.217 Zone dma32 velocity 0.000 0.000 Zone dma velocity 0.000 0.000 Page writes by reclaim 89764.000 105233.000 Page writes file 46 533 Page writes anon 89718 104700 Page reclaim immediate 21457 3699 Sector Reads 3259688 3441368 Sector Writes 3667252 3754836 Page rescued immediate 0 0 Slabs scanned 1042872 1160855 Direct inode steals 8042 10089 Kswapd inode steals 54295 29170 Kswapd skipped wait 0 0 THP fault alloc 175 154 THP collapse alloc 226 289 THP splits 0 0 THP fault fallback 11 14 THP collapse fail 3 2 Compaction stalls 536 646 Compaction success 322 358 Compaction failures 214 288 Page migrate success 119608 111063 Page migrate failure 2723 2593 Compaction pages isolated 250179 232652 Compaction migrate scanned 9131832 9942306 Compaction free scanned 2093272 2613998 Compaction cost 192 189 NUMA alloc hit 47124555 47193990 NUMA alloc miss 0 0 NUMA interleave hit 0 0 NUMA alloc local 47124555 47193990 NUMA base PTE updates 0 0 NUMA huge PMD updates 0 0 NUMA page range updates 0 0 NUMA hint faults 0 0 NUMA hint local faults 0 0 NUMA hint local percent 100 100 NUMA pages migrated 0 0 AutoNUMA cost 0% 0% [akpm@xxxxxxxxxxxxxxxxxxxx: remove newline, per Minchan] Link: http://lkml.kernel.org/r/1500889535-19648-1-git-send-email-zhuhui@xxxxxxxxxx Signed-off-by: Hui Zhu <zhuhui@xxxxxxxxxx> Acked-by: Minchan Kim <minchan@xxxxxxxxxx> Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@xxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/zsmalloc.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff -puN mm/zsmalloc.c~zsmalloc-zs_page_migrate-skip-unnecessary-loops-but-not-return-ebusy-if-zspage-is-not-inuse mm/zsmalloc.c --- a/mm/zsmalloc.c~zsmalloc-zs_page_migrate-skip-unnecessary-loops-but-not-return-ebusy-if-zspage-is-not-inuse +++ a/mm/zsmalloc.c @@ -1983,8 +1983,11 @@ int zs_page_migrate(struct address_space spin_lock(&class->lock); if (!get_zspage_inuse(zspage)) { - ret = -EBUSY; - goto unlock_class; + /* + * Set "offset" to end of the page so that every loops + * skips unnecessary object scanning. + */ + offset = PAGE_SIZE; } pos = offset; @@ -2052,7 +2055,6 @@ unpin_objects: } } kunmap_atomic(s_addr); -unlock_class: spin_unlock(&class->lock); migrate_write_unlock(zspage); _ -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
