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authorSong Liu <songliubraving@fb.com>2017-01-24 23:08:23 +0100
committerShaohua Li <shli@fb.com>2017-02-13 18:17:52 +0100
commit39b99586b321a9cbd4fe9abb5ea9346d2c4ca9c6 (patch)
tree8c4d3a516260a209f968c3d1755575433401340e /net/rds
parentmd/r5cache: enable chunk_aligned_read with write back cache (diff)
downloadlinux-39b99586b321a9cbd4fe9abb5ea9346d2c4ca9c6.tar.xz
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md/r5cache: improve journal device efficiency
It is important to be able to flush all stripes in raid5-cache. Therefore, we need reserve some space on the journal device for these flushes. If flush operation includes pending writes to the stripe, we need to reserve (conf->raid_disk + 1) pages per stripe for the flush out. This reduces the efficiency of journal space. If we exclude these pending writes from flush operation, we only need (conf->max_degraded + 1) pages per stripe. With this patch, when log space is critical (R5C_LOG_CRITICAL=1), pending writes will be excluded from stripe flush out. Therefore, we can reduce reserved space for flush out and thus improve journal device efficiency. Signed-off-by: Song Liu <songliubraving@fb.com> Signed-off-by: Shaohua Li <shli@fb.com>
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