kernel_optimize_test/mm
Huang Ying cbc65df240 mm, swap: add swap readahead hit statistics
Patch series "mm, swap: VMA based swap readahead", v4.

The swap readahead is an important mechanism to reduce the swap in
latency.  Although pure sequential memory access pattern isn't very
popular for anonymous memory, the space locality is still considered
valid.

In the original swap readahead implementation, the consecutive blocks in
swap device are readahead based on the global space locality estimation.
But the consecutive blocks in swap device just reflect the order of page
reclaiming, don't necessarily reflect the access pattern in virtual
memory space.  And the different tasks in the system may have different
access patterns, which makes the global space locality estimation
incorrect.

In this patchset, when page fault occurs, the virtual pages near the
fault address will be readahead instead of the swap slots near the fault
swap slot in swap device.  This avoid to readahead the unrelated swap
slots.  At the same time, the swap readahead is changed to work on
per-VMA from globally.  So that the different access patterns of the
different VMAs could be distinguished, and the different readahead
policy could be applied accordingly.  The original core readahead
detection and scaling algorithm is reused, because it is an effect
algorithm to detect the space locality.

In addition to the swap readahead changes, some new sysfs interface is
added to show the efficiency of the readahead algorithm and some other
swap statistics.

This new implementation will incur more small random read, on SSD, the
improved correctness of estimation and readahead target should beat the
potential increased overhead, this is also illustrated in the test
results below.  But on HDD, the overhead may beat the benefit, so the
original implementation will be used by default.

The test and result is as follow,

Common test condition
=====================

Test Machine: Xeon E5 v3 (2 sockets, 72 threads, 32G RAM)
Swap device: NVMe disk

Micro-benchmark with combined access pattern
============================================

vm-scalability, sequential swap test case, 4 processes to eat 50G
virtual memory space, repeat the sequential memory writing until 300
seconds.  The first round writing will trigger swap out, the following
rounds will trigger sequential swap in and out.

At the same time, run vm-scalability random swap test case in
background, 8 processes to eat 30G virtual memory space, repeat the
random memory write until 300 seconds.  This will trigger random swap-in
in the background.

This is a combined workload with sequential and random memory accessing
at the same time.  The result (for sequential workload) is as follow,

			Base		Optimized
			----		---------
throughput		345413 KB/s	414029 KB/s (+19.9%)
latency.average		97.14 us	61.06 us (-37.1%)
latency.50th		2 us		1 us
latency.60th		2 us		1 us
latency.70th		98 us		2 us
latency.80th		160 us		2 us
latency.90th		260 us		217 us
latency.95th		346 us		369 us
latency.99th		1.34 ms		1.09 ms
ra_hit%			52.69%		99.98%

The original swap readahead algorithm is confused by the background
random access workload, so readahead hit rate is lower.  The VMA-base
readahead algorithm works much better.

Linpack
=======

The test memory size is bigger than RAM to trigger swapping.

			Base		Optimized
			----		---------
elapsed_time		393.49 s	329.88 s (-16.2%)
ra_hit%			86.21%		98.82%

The score of base and optimized kernel hasn't visible changes.  But the
elapsed time reduced and readahead hit rate improved, so the optimized
kernel runs better for startup and tear down stages.  And the absolute
value of readahead hit rate is high, shows that the space locality is
still valid in some practical workloads.

This patch (of 5):

The statistics for total readahead pages and total readahead hits are
recorded and exported via the following sysfs interface.

/sys/kernel/mm/swap/ra_hits
/sys/kernel/mm/swap/ra_total

With them, the efficiency of the swap readahead could be measured, so
that the swap readahead algorithm and parameters could be tuned
accordingly.

[akpm@linux-foundation.org: don't display swap stats if CONFIG_SWAP=n]
Link: http://lkml.kernel.org/r/20170807054038.1843-2-ying.huang@intel.com
Signed-off-by: "Huang, Ying" <ying.huang@intel.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Shaohua Li <shli@kernel.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: Fengguang Wu <fengguang.wu@intel.com>
Cc: Tim Chen <tim.c.chen@intel.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2017-09-06 17:27:29 -07:00
..
kasan Merge branch 'linus' into locking/core, to pick up fixes 2017-08-10 12:20:53 +02:00
backing-dev.c bdi: Drop 'parent' argument from bdi_register[_va]() 2017-04-20 12:09:55 -06:00
balloon_compaction.c mm/balloon_compaction.c: don't zero ballooned pages 2017-08-10 15:54:07 -07:00
bootmem.c mm/bootmem.c: cosmetic improvement of code readability 2017-02-22 16:41:29 -08:00
cleancache.c fs: switch ->s_uuid to uuid_t 2017-06-05 16:59:12 +02:00
cma_debug.c mm/cma_debug.c: fix stack corruption due to sprintf usage 2017-08-18 15:32:02 -07:00
cma.c cma: fix calculation of aligned offset 2017-07-10 16:32:32 -07:00
cma.h cma: Store a name in the cma structure 2017-04-18 20:41:12 +02:00
compaction.c mm, compaction: skip over holes in __reset_isolation_suitable 2017-07-06 16:24:32 -07:00
debug_page_ref.c
debug.c mm: make tlb_flush_pending global 2017-08-10 15:54:07 -07:00
dmapool.c lib/vsprintf.c: remove %Z support 2017-02-27 18:43:47 -08:00
early_ioremap.c x86/mm: Add support to access boot related data in the clear 2017-07-18 11:38:02 +02:00
fadvise.c
failslab.c
filemap.c mm: use find_get_pages_range() in filemap_range_has_page() 2017-09-06 17:27:27 -07:00
frame_vector.c treewide: use kv[mz]alloc* rather than opencoded variants 2017-05-08 17:15:13 -07:00
frontswap.c
gup.c mm/gup: make __gup_device_* require THP 2017-09-06 17:27:26 -07:00
highmem.c
huge_memory.c mm, THP, swap: support splitting THP for THP swap out 2017-09-06 17:27:28 -07:00
hugetlb_cgroup.c
hugetlb.c mm, hugetlb: do not allocate non-migrateable gigantic pages from movable zones 2017-09-06 17:27:29 -07:00
hwpoison-inject.c mm: hwpoison: call shake_page() unconditionally 2017-05-03 15:52:12 -07:00
init-mm.c
internal.h mm, memory_hotplug: drop zone from build_all_zonelists 2017-09-06 17:27:25 -07:00
interval_tree.c
Kconfig mm, devm_memremap_pages: use multi-order radix for ZONE_DEVICE lookups 2017-09-06 17:27:29 -07:00
Kconfig.debug mm: enable page poisoning early at boot 2017-05-03 15:52:10 -07:00
khugepaged.c mm: make PR_SET_THP_DISABLE immediately active 2017-07-10 16:32:31 -07:00
kmemcheck.c mm: Rename SLAB_DESTROY_BY_RCU to SLAB_TYPESAFE_BY_RCU 2017-04-18 11:42:36 -07:00
kmemleak-test.c
kmemleak.c mm: kmemleak: treat vm_struct as alternative reference to vmalloc'ed objects 2017-07-06 16:24:34 -07:00
ksm.c mm/ksm.c: constify attribute_group structures 2017-09-06 17:27:27 -07:00
list_lru.c mm/list_lru.c: fix list_lru_count_node() to be race free 2017-07-10 16:32:33 -07:00
maccess.c
madvise.c mm, madvise: ensure poisoned pages are removed from per-cpu lists 2017-08-31 16:33:15 -07:00
Makefile percpu: expose statistics about percpu memory via debugfs 2017-06-20 15:31:38 -04:00
memblock.c mm/memblock.c: reversed logic in memblock_discard() 2017-08-25 16:12:46 -07:00
memcontrol.c memcg, THP, swap: make mem_cgroup_swapout() support THP 2017-09-06 17:27:28 -07:00
memory_hotplug.c mm, memory_hotplug: get rid of zonelists_mutex 2017-09-06 17:27:26 -07:00
memory-failure.c x86/mm, mm/hwpoison: Clear PRESENT bit for kernel 1:1 mappings of poison pages 2017-08-17 10:30:49 +02:00
memory.c mm, THP, swap: make reuse_swap_page() works for THP swapped out 2017-09-06 17:27:27 -07:00
mempolicy.c mm/mempolicy: fix use after free when calling get_mempolicy 2017-08-18 15:32:02 -07:00
mempool.c sched/wait: Rename wait_queue_t => wait_queue_entry_t 2017-06-20 12:18:27 +02:00
memtest.c
migrate.c Sanitize 'move_pages()' permission checks 2017-08-20 13:26:27 -07:00
mincore.c mm: remove shmem_mapping() shmem_zero_setup() duplicates 2017-02-24 17:46:56 -08:00
mlock.c mlock: fix mlock count can not decrease in race condition 2017-06-02 15:07:38 -07:00
mm_init.c
mmap.c userfaultfd: call userfaultfd_unmap_prep only if __split_vma succeeds 2017-09-06 17:27:29 -07:00
mmu_context.c sched/headers: Prepare to move the task_lock()/unlock() APIs to <linux/sched/task.h> 2017-03-02 08:42:38 +01:00
mmu_notifier.c mm/mmu_notifier: kill invalidate_page 2017-08-31 16:13:00 -07:00
mmzone.c mm/mmzone.c: swap likely to unlikely as code logic is different for next_zones_zonelist() 2017-02-22 16:41:29 -08:00
mprotect.c mm: migrate: prevent racy access to tlb_flush_pending 2017-08-10 15:54:07 -07:00
mremap.c mm/mremap: fail map duplication attempts for private mappings 2017-09-06 17:27:26 -07:00
msync.c
nobootmem.c mm: discard memblock data later 2017-08-18 15:32:01 -07:00
nommu.c mm: rename global_page_state to global_zone_page_state 2017-09-06 17:27:29 -07:00
oom_kill.c mm/oom_kill.c: add tracepoints for oom reaper-related events 2017-07-10 16:32:32 -07:00
page_alloc.c mm: rename global_page_state to global_zone_page_state 2017-09-06 17:27:29 -07:00
page_counter.c
page_ext.c mm, page_ext: periodically reschedule during page_ext_init() 2017-09-06 17:27:26 -07:00
page_idle.c mm/page_idle.c: constify attribute_group structures 2017-09-06 17:27:27 -07:00
page_io.c mm: test code to write THP to swap device as a whole 2017-09-06 17:27:28 -07:00
page_isolation.c mm: unify new_node_page and alloc_migrate_target 2017-07-10 16:32:31 -07:00
page_owner.c mm, page_owner: don't grab zone->lock for init_pages_in_zone() 2017-09-06 17:27:26 -07:00
page_poison.c mm: enable page poisoning early at boot 2017-05-03 15:52:10 -07:00
page_vma_mapped.c mm/hugetlb: add size parameter to huge_pte_offset() 2017-07-06 16:24:34 -07:00
page-writeback.c mm: rename global_page_state to global_zone_page_state 2017-09-06 17:27:29 -07:00
pagewalk.c mm/hugetlb: add size parameter to huge_pte_offset() 2017-07-06 16:24:34 -07:00
percpu-internal.h percpu: fix early calls for spinlock in pcpu_stats 2017-06-21 13:53:52 -04:00
percpu-km.c percpu: fix static checker warnings in pcpu_destroy_chunk 2017-06-29 11:23:38 -04:00
percpu-stats.c percpu: expose statistics about percpu memory via debugfs 2017-06-20 15:31:38 -04:00
percpu-vm.c percpu: fix static checker warnings in pcpu_destroy_chunk 2017-06-29 11:23:38 -04:00
percpu.c percpu: resolve err may not be initialized in pcpu_alloc 2017-06-21 12:00:45 -04:00
pgtable-generic.c mm: convert generic code to 5-level paging 2017-03-09 11:48:47 -08:00
process_vm_access.c sched/headers: Prepare for new header dependencies before moving code to <linux/sched/mm.h> 2017-03-02 08:42:28 +01:00
quicklist.c
readahead.c
rmap.c mm/rmap: update to new mmu_notifier semantic v2 2017-08-31 16:12:59 -07:00
rodata_test.c mm: remove rodata_test_data export, add pr_fmt 2017-05-03 15:52:09 -07:00
shmem.c mm/shmem: add hugetlbfs support to memfd_create() 2017-09-06 17:27:29 -07:00
slab_common.c mm: allow slab_nomerge to be set at build time 2017-07-06 16:24:31 -07:00
slab.c mm: memcontrol: account slab stats per lruvec 2017-07-06 16:24:35 -07:00
slab.h locking/lockdep: Rework FS_RECLAIM annotation 2017-08-10 12:29:03 +02:00
slob.c locking/lockdep: Rework FS_RECLAIM annotation 2017-08-10 12:29:03 +02:00
slub.c mm/slub.c: constify attribute_group structures 2017-09-06 17:27:27 -07:00
sparse-vmemmap.c mm, sparse, page_ext: drop ugly N_HIGH_MEMORY branches for allocations 2017-09-06 17:27:26 -07:00
sparse.c mm, sparse, page_ext: drop ugly N_HIGH_MEMORY branches for allocations 2017-09-06 17:27:26 -07:00
swap_cgroup.c mm, THP, swap: delay splitting THP during swap out 2017-07-06 16:24:31 -07:00
swap_slots.c mm/swap_slots.c: don't disable preemption while taking the per-CPU cache 2017-07-10 16:32:32 -07:00
swap_state.c mm, swap: add swap readahead hit statistics 2017-09-06 17:27:29 -07:00
swap.c mm: remove nr_pages argument from pagevec_lookup{,_range}() 2017-09-06 17:27:27 -07:00
swapfile.c mm, THP, swap: support splitting THP for THP swap out 2017-09-06 17:27:28 -07:00
truncate.c mm/truncate.c: fix THP handling in invalidate_mapping_pages() 2017-07-10 16:32:32 -07:00
usercopy.c mm/usercopy: Drop extra is_vmalloc_or_module() check 2017-04-05 12:30:18 -07:00
userfaultfd.c userfaultfd: shmem: wire up shmem_mfill_zeropage_pte 2017-09-06 17:27:28 -07:00
util.c mm: rename global_page_state to global_zone_page_state 2017-09-06 17:27:29 -07:00
vmacache.c sched/headers: Prepare to move 'init_task' and 'init_thread_union' from <linux/sched.h> to <linux/sched/task.h> 2017-03-02 08:42:38 +01:00
vmalloc.c mm/vmalloc.c: don't reinvent the wheel but use existing llist API 2017-09-06 17:27:29 -07:00
vmpressure.c mm, vmpressure: pass-through notification support 2017-07-10 16:32:31 -07:00
vmscan.c mm, THP, swap: add THP swapping out fallback counting 2017-09-06 17:27:28 -07:00
vmstat.c mm, swap: add swap readahead hit statistics 2017-09-06 17:27:29 -07:00
workingset.c mm: memcontrol: per-lruvec stats infrastructure 2017-07-06 16:24:35 -07:00
z3fold.c z3fold: fix page locking in z3fold_alloc() 2017-04-13 18:24:20 -07:00
zbud.c
zpool.c
zsmalloc.c zsmalloc: zs_page_migrate: skip unnecessary loops but not return -EBUSY if zspage is not inuse 2017-09-06 17:27:26 -07:00
zswap.c mm/zswap.c: delete an error message for a failed memory allocation in zswap_dstmem_prepare() 2017-07-06 16:24:35 -07:00