linux - 在 Linux 系统上保留大页面

Question

我的 VMWare guest 系统详细信息:

Linux 2.6.32-358.el6.x86_64 (RH 6.4 - Santiago)

# cat /proc/meminfo
MemTotal:        8058796 kB
MemFree:         5145692 kB
Buffers:           32320 kB
Cached:           291312 kB
SwapCached:            0 kB
Active:          1524652 kB
Inactive:         192444 kB
Active(anon):    1393628 kB
Inactive(anon):     1196 kB
Active(file):     131024 kB
Inactive(file):   191248 kB
Unevictable:           0 kB
Mlocked:               0 kB
SwapTotal:       4063224 kB
SwapFree:        4063224 kB
Dirty:               144 kB
Writeback:             0 kB
AnonPages:       1393488 kB
Mapped:            47288 kB
Shmem:              1364 kB
Slab:              52080 kB
SReclaimable:      18572 kB
SUnreclaim:        33508 kB
KernelStack:        3776 kB
PageTables:        15864 kB
NFS_Unstable:          0 kB
Bounce:                0 kB
WritebackTmp:          0 kB
CommitLimit:     4063224 kB
Committed_AS:    3101408 kB
VmallocTotal:   34359738367 kB
VmallocUsed:      160248 kB
VmallocChunk:   34359572656 kB
HardwareCorrupted:     0 kB
AnonHugePages:         0 kB
HugePages_Total:     512
HugePages_Free:      240
HugePages_Rsvd:      240
HugePages_Surp:        0
Hugepagesize:       2048 kB
DirectMap4k:       10240 kB
DirectMap2M:     8378368 kB

grub contents:
transparent_hugepage=never default_hugepagesz=2M hugepagesz=2M hugepages=512

# sysctl -a | grep vm
vm.overcommit_memory = 0
vm.panic_on_oom = 0
vm.oom_kill_allocating_task = 0
vm.extfrag_threshold = 500
vm.oom_dump_tasks = 1
vm.would_have_oomkilled = 0
vm.overcommit_ratio = 0
vm.page-cluster = 3
vm.dirty_background_ratio = 10
vm.dirty_background_bytes = 0
vm.dirty_ratio = 20
vm.dirty_bytes = 0
vm.dirty_writeback_centisecs = 500
vm.dirty_expire_centisecs = 3000
vm.nr_pdflush_threads = 0
vm.swappiness = 60
vm.nr_hugepages = 512
vm.nr_hugepages_mempolicy = 512
vm.hugetlb_shm_group = 0
vm.hugepages_treat_as_movable = 0
vm.nr_overcommit_hugepages = 0
vm.lowmem_reserve_ratio = 256   256     32
vm.drop_caches = 0
vm.min_free_kbytes = 2048
vm.extra_free_kbytes = 0
vm.percpu_pagelist_fraction = 0
vm.max_map_count = 65530
vm.laptop_mode = 0
vm.block_dump = 0
vm.vfs_cache_pressure = 100
vm.legacy_va_layout = 0
vm.zone_reclaim_mode = 0
vm.min_unmapped_ratio = 1
vm.min_slab_ratio = 5
vm.stat_interval = 1
vm.mmap_min_addr = 4096
vm.numa_zonelist_order = default
vm.scan_unevictable_pages = 0
vm.memory_failure_early_kill = 0
vm.memory_failure_recovery = 1

我的应用程序在启动时需要尽可能多地获取大页面，但 HugePages_Free 等于 HugePages_Rsvd 这一事实意味着它无法保留任何大页面。

这是什么原因，如果有的话，如何禁用其他应用程序对大页面的保留？

谢谢

Answer 1

What is the reason for this, and how do I disable the reservation of hugepages by other applications, if there are any?

这是因为 Linux 使用 Huge Pages 进行分配和内存映射。请查看 mmmap(2)(MAP_HUGETLB 标志)、madvice(2)(MADV_HUGEPAGE 标志)和透明大页面:

https://www.kernel.org/doc/Documentation/vm/transhuge.txt

基本上，这是因为在您的系统上运行的任何应用程序都可能要求系统使用大页面，甚至 Linux 本身也可能透明地将您分配给大页面。

因此，要禁用所有这些隐式用法，您可以查看/sys/kernel/mm/transparent_hugepage/enabled

另一方面，您可能会考虑在应用程序启动之前分配大页面。在没有任何大页面的情况下运行系统，然后配置它们:

echo 512 > /proc/sys/vm/nr_hugepages

并立即运行您的应用程序。这将增加大页面仅供您的应用程序使用的可能性。