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sysctl
huge pages
sysctl vm.nr_hugepages=32 cat /proc/meminfo HugePages_Total: 95 HugePages_Free: 72 HugePages_Rsvd: 0 HugePages_Surp: 0 Hugepagesize: 2048 kB Hugetlb: 194560 kB
fs writes - dirty cache
Low write performance on Linux servers with large RAM
# Contains the amount of dirty memory at which the background kernel flusher threads will start writeback. # Note: # dirty_background_bytes is the counterpart of dirty_background_ratio. # Only one of them may be specified at a time. When one sysctl is written it is immediately taken into # account to evaluate the dirty memory limits and the other appears as 0 when read.
vm.dirty_background_bytes = 0 vm.dirty_background_ratio = 10
# Contains the amount of dirty memory at which a process generating disk writes will itself start writeback. # Note: dirty_bytes is the counterpart of dirty_ratio. Only one of them may be specified at a time. # When one sysctl is written it is immediately taken into account to evaluate #the dirty memory limits and the other appears as 0 when read. vm.dirty_bytes = 0
# Contains, as a percentage of total available memory that contains free pages and reclaimable pages, # the number of pages at which a process which is generating disk writes will itself start writing out dirty data. vm.dirty_ratio = 20
# This tunable is used to define when dirty data is old enough to be eligible for writeout by the kernel flusher threads. vm.dirty_expire_centisecs = 3000
# The kernel flusher threads will periodically wake up and write old data out to disk. vm.dirty_writeback_centisecs = 500