Use 10s periodic writeback

Signed-off-by: Tyler Nijmeh <tylernij@gmail.com>

README.md

@@ -125,8 +125,8 @@ This tunable is the same as the former, but it is the ceiling for **synchronous*
 ### vm.dirty_expire_centisecs: 300 (3s) --> 1000 (10s)
 This is the longest that dirty pages can remain in the system before they are forcefully written out to the disk. By increasing this value, we can allow the dirty background writeback to take its time asynchronously, and avoid unnecessary writebacks that can clog the flusher thread.
 
-### vm.dirty_writeback_centisecs: 500 (5s) --> 0 (0s)
-Do not periodically writeback data every 5 seconds. Instead, leave it to the dirty background writeback to wake up when the dirty memory of the system hits 10%. This allows the dirty pages to stay in memory for longer, possibly increasing cache locality as the page cache is still available in memory.
+### vm.dirty_writeback_centisecs: 500 (5s) --> 1000 (10s)
+Do the periodic writeback less often to keep dirty memory available for longer. This goes hand-in-hand with the previous tweak.
 
 ### vm.extfrag_threshold: 500 --> 750
 Compact memory more often, even if the memory allocation was estimated to be due to a low-memory status. This lets us put more data into RAM at the expense of running compation more often. This is a worthy tradeoff, as it reduces memory fragmentation, which is incredibly important for ZRAM.

system/bin/ktweak

@@ -149,7 +149,7 @@ ctl vm.compact_unevictable_allowed 0
 ctl vm.dirty_background_ratio 10
 ctl vm.dirty_ratio 30
 ctl vm.dirty_expire_centisecs 1000
-ctl vm.dirty_writeback_centisecs 0
+ctl vm.dirty_writeback_centisecs 1000
 ctl vm.extfrag_threshold 750
 ctl vm.oom_dump_tasks 0
 ctl vm.page-cluster 0