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linux:kernel:sysctl [2021/03/01 21:08] – created niziaklinux:kernel:sysctl [2025/03/23 11:20] (current) – niziak
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 Hugetlb:          194560 kB Hugetlb:          194560 kB
 </code> </code>
 +
 +===== fs writes - dirty cache =====
 +
 +[[https://www.suse.com/support/kb/doc/?id=000017857|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
 +
 +
 +
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 +