diff options
| -rw-r--r-- | man/man4/zfs.4 | 14 | ||||
| -rw-r--r-- | module/zfs/arc.c | 11 |
2 files changed, 18 insertions, 7 deletions
diff --git a/man/man4/zfs.4 b/man/man4/zfs.4 index 717cf8e6e..c17bfb80b 100644 --- a/man/man4/zfs.4 +++ b/man/man4/zfs.4 @@ -121,20 +121,26 @@ Controls whether buffers present on special vdevs are eligible for caching into L2ARC. If set to 1, exclude dbufs on special vdevs from being cached to L2ARC. . -.It Sy l2arc_mfuonly Ns = Ns Sy 0 Ns | Ns 1 Pq int +.It Sy l2arc_mfuonly Ns = Ns Sy 0 Ns | Ns 1 Ns | Ns 2 Pq int Controls whether only MFU metadata and data are cached from ARC into L2ARC. This may be desired to avoid wasting space on L2ARC when reading/writing large amounts of data that are not expected to be accessed more than once. .Pp -The default is off, +The default is 0, meaning both MRU and MFU data and metadata are cached. -When turning off this feature, some MRU buffers will still be present -in ARC and eventually cached on L2ARC. +When turning off this feature (setting it to 0), some MRU buffers will +still be present in ARC and eventually cached on L2ARC. .No If Sy l2arc_noprefetch Ns = Ns Sy 0 , some prefetched buffers will be cached to L2ARC, and those might later transition to MRU, in which case the .Sy l2arc_mru_asize No arcstat will not be Sy 0 . .Pp +Setting it to 1 means to L2 cache only MFU data and metadata. +.Pp +Setting it to 2 means to L2 cache all metadata (MRU+MFU) but +only MFU data (ie: MRU data are not cached). This can be the right setting +to cache as much metadata as possible even when having high data turnover. +.Pp Regardless of .Sy l2arc_noprefetch , some MFU buffers might be evicted from ARC, diff --git a/module/zfs/arc.c b/module/zfs/arc.c index f25afa312..d7ee9d32a 100644 --- a/module/zfs/arc.c +++ b/module/zfs/arc.c @@ -9055,12 +9055,17 @@ l2arc_write_buffers(spa_t *spa, l2arc_dev_t *dev, uint64_t target_sz) */ for (int pass = 0; pass < L2ARC_FEED_TYPES; pass++) { /* - * If pass == 1 or 3, we cache MRU metadata and data - * respectively. + * pass == 0: MFU meta + * pass == 1: MRU meta + * pass == 2: MFU data + * pass == 3: MRU data */ - if (l2arc_mfuonly) { + if (l2arc_mfuonly == 1) { if (pass == 1 || pass == 3) continue; + } else if (l2arc_mfuonly > 1) { + if (pass == 3) + continue; } uint64_t passed_sz = 0; |