Don't use MADV_RANDOM #940
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CC @dusk125 |
In addition to the explicit documented behavior in posix_madvise(2) this call since Linux 6.4 also causes the kernel to aggressively free pages from the page cache by short circuiting the LRU second chance mechanism. The result is compaction events that took 900ms now take up to 20s and a system which generally operated with near zero major page faults sees 600 or more major faults per second during compaction events. We've tested this change in older kernels and observed no negative impact in typical cloud instances. Fixes etcd-io#939
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In addition to the explicit documented behavior in posix_madvise(2) this
call since Linux 6.4 also causes the kernel to aggressively free pages
from the page cache by short circuiting the LRU second chance mechanism.
The result is compaction events that took 900ms now take up to 20s and
a system which generally operated with near zero major page faults sees
600 or more major faults per second during compaction events.
We've tested this change in older kernels and observed no negative impact
in typical cloud instances.
Fixes #939