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Introduce ZFS module parameter l2arc_mfuonly

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In certain workloads it may be beneficial to reduce wear of L2ARC
devices by not caching MRU metadata and data into L2ARC. This commit
introduces a new tunable l2arc_mfuonly for this purpose.

Reviewed-by: Matthew Ahrens <mahrens@delphix.com>
Reviewed-by: Richard Elling <Richard.Elling@RichardElling.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: George Amanakis <gamanakis@gmail.com>
Closes #10710
This commit is contained in:
George Amanakis 2020-09-08 14:44:37 -04:00 committed by Brian Behlendorf
parent 127daad223
commit 78d84f56d1
2 changed files with 34 additions and 0 deletions
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16
man/man5/zfs-module-parameters.5
View File

@ -198,6 +198,22 @@ feature.
Default value: \fB200\fR%.
.RE
.sp
.ne 2
.na
\fBl2arc_mfuonly\fR (int)
.ad
.RS 12n
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. The
default is \fB0\fR, meaning both MRU and MFU data and metadata are cached.
When turning off (\fB0\fR) this feature some MRU buffers will still be present
in ARC and eventually cached on L2ARC.
.sp
Use \fB0\fR for no (default) and \fB1\fR for yes.
.RE
.sp
.ne 2
.na

18
module/zfs/arc.c
View File

@ -894,6 +894,12 @@ static boolean_t l2arc_write_eligible(uint64_t, arc_buf_hdr_t *);
static void l2arc_read_done(zio_t *);
static void l2arc_do_free_on_write(void);
/*
* l2arc_mfuonly : A ZFS module parameter that controls whether only MFU
* metadata and data are cached from ARC into L2ARC.
*/
int l2arc_mfuonly = 0;
/*
* L2ARC TRIM
* l2arc_trim_ahead : A ZFS module parameter that controls how much ahead of
@ -8909,6 +8915,15 @@ l2arc_write_buffers(spa_t *spa, l2arc_dev_t *dev, uint64_t target_sz)
* Copy buffers for L2ARC writing.
*/
for (int try = 0; try < L2ARC_FEED_TYPES; try++) {
/*
* If try == 1 or 3, we cache MRU metadata and data
* respectively.
*/
if (l2arc_mfuonly) {
if (try == 1 || try == 3)
continue;
}
multilist_sublist_t *mls = l2arc_sublist_lock(try);
uint64_t passed_sz = 0;
@ -10562,6 +10577,9 @@ ZFS_MODULE_PARAM(zfs_l2arc, l2arc_, rebuild_enabled, INT, ZMOD_RW,
ZFS_MODULE_PARAM(zfs_l2arc, l2arc_, rebuild_blocks_min_l2size, ULONG, ZMOD_RW,
"Min size in bytes to write rebuild log blocks in L2ARC");
ZFS_MODULE_PARAM(zfs_l2arc, l2arc_, mfuonly, INT, ZMOD_RW,
"Cache only MFU data from ARC into L2ARC");
ZFS_MODULE_PARAM_CALL(zfs_arc, zfs_arc_, lotsfree_percent, param_set_arc_int,
param_get_int, ZMOD_RW, "System free memory I/O throttle in bytes");