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** Changed in: linux (Ubuntu)
Status: New => Incomplete
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https://bugs.launchpad.net/bugs/1811277
Title:
GCE: RAID6_PQ module adds boot latency - can RAID6_PQ be provided as a
module
Status in linux package in Ubuntu:
Incomplete
Bug description:
Google reports: For a n1-standard-2 with ubuntu-1604, we spend around
600 milliseconds during boot on computing the best raid6 recovery
algorithm seen in the following lines of the kernel logs:
...
[ 2.216022] raid6: sse2x1 gen() 8570 MB/s
[ 2.264029] raid6: sse2x1 xor() 6467 MB/s
[ 2.312030] raid6: sse2x2 gen() 10602 MB/s
[ 2.360021] raid6: sse2x2 xor() 6999 MB/s
[ 2.412028] raid6: sse2x4 gen() 12483 MB/s
[ 2.464022] raid6: sse2x4 xor() 8607 MB/s
[ 2.516024] raid6: avx2x1 gen() 16712 MB/s
[ 2.568020] raid6: avx2x1 xor() 12050 MB/s
[ 2.620019] raid6: avx2x2 gen() 19393 MB/s
[ 2.672024] raid6: avx2x2 xor() 12406 MB/s
[ 2.724034] raid6: avx2x4 gen() 22330 MB/s
[ 2.776029] raid6: avx2x4 xor() 15196 MB/s
[ 2.780440] raid6: using algorithm avx2x4 gen() 22330 MB/s
[ 2.786035] raid6: .... xor() 15196 MB/s, rmw enabled
[ 2.791196] raid6: using avx2x2 recovery algorithm
...
This raid6 computation is a result of including the raid6_pq module
statically. Based on the output of `lsmod`, is there any reason this
couldn't just be used as a module?
ryanrose@ryanrose-boottimes-ubuntu16-test:~$ lsmod
Module Size Used by
...
btrfs 1101824 0
raid10 49152 0
raid456 143360 0
async_raid6_recov 20480 1 raid456
async_memcpy 16384 2 raid456,async_raid6_recov
async_pq 16384 2 raid456,async_raid6_recov
async_xor 16384 3 async_pq,raid456,async_raid6_recov
async_tx 16384 5 async_xor,async_pq,raid456,async_memcpy,async_raid6_recov
xor 24576 2 async_xor,btrfs
raid6_pq 118784 4 async_pq,btrfs,raid456,async_raid6_recov
raid1 40960 0
raid0 20480 0
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