Assume that reads and writes to the variable will be atomic. The worse
that could happen is that one of the purges removes a partially
written percentage of grants, but the cache itself will recover.
Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
---
Cc: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
Cc: Jens Axboe <axboe@xxxxxxxxx>
Cc: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
Cc: SeongJae Park <sjpark@xxxxxxxxx>
Cc: xen-devel@xxxxxxxxxxxxxxxxxxxx
Cc: linux-block@xxxxxxxxxxxxxxx
Cc: J. Roeleveld <joost@xxxxxxxxxxxx>
Cc: Jürgen Groß <jgross@xxxxxxxx>
---
Documentation/ABI/testing/sysfs-driver-xen-blkback | 9 +++++++++
drivers/block/xen-blkback/blkback.c | 7 +++++--
2 files changed, 14 insertions(+), 2 deletions(-)
diff --git a/Documentation/ABI/testing/sysfs-driver-xen-blkback b/Documentation/ABI/testing/sysfs-driver-xen-blkback
index 776f25d335ca..7de791ad61f9 100644
--- a/Documentation/ABI/testing/sysfs-driver-xen-blkback
+++ b/Documentation/ABI/testing/sysfs-driver-xen-blkback
@@ -45,3 +45,12 @@ Description:
to be executed periodically. This parameter controls the time
interval between consecutive executions of the purge mechanism
is set in ms.
+
+What: /sys/module/xen_blkback/parameters/lru_percent_clean
+Date: October 2020
+KernelVersion: 5.10
+Contact: Roger Pau Monné <roger.pau@xxxxxxxxxx>
+Description:
+ When the persistent grants list is full we will remove unused
+ grants from the list. The percent number of grants to be
+ removed at each LRU execution.
diff --git a/drivers/block/xen-blkback/blkback.c b/drivers/block/xen-blkback/blkback.c
index 6ad9b76fdb2b..772852d45a5a 100644
--- a/drivers/block/xen-blkback/blkback.c
+++ b/drivers/block/xen-blkback/blkback.c
@@ -127,7 +127,10 @@ MODULE_PARM_DESC(lru_internval,
* from the list. The percent number of grants to be removed at each LRU
* execution.
*/
-#define LRU_PERCENT_CLEAN 5
+static unsigned int lru_percent_clean = 5;
+module_param_named(lru_percent_clean, lru_percent_clean, uint, 0644);
+MODULE_PARM_DESC(lru_percent_clean,
+ "Percentage of persistent grants to remove from the cache when full");
/* Run-time switchable: /sys/module/blkback/parameters/ */
static unsigned int log_stats;
@@ -404,7 +407,7 @@ static void purge_persistent_gnt(struct xen_blkif_ring *ring)
!ring->blkif->vbd.overflow_max_grants)) {
num_clean = 0;
} else {
- num_clean = (max_pgrants / 100) * LRU_PERCENT_CLEAN;
+ num_clean = (max_pgrants / 100) * lru_percent_clean;
num_clean = ring->persistent_gnt_c - max_pgrants + num_clean;
num_clean = min(ring->persistent_gnt_c, num_clean);
pr_debug("Going to purge at least %u persistent grants\n",
--
2.28.0
