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....@citrix.com>
---
Cc: Konrad Rzeszutek Wilk <konrad.w...@oracle.com>
Cc: Jens Axboe <ax...@kernel.dk>
Cc: Boris Ostrovsky <boris.ostrov...@oracle.com>
Cc: SeongJae Park <sjp...@amazon.de>
Cc: xen-de...@lists.xenproject.org
Cc: linux-bl...@vger.kernel.org
Cc: J. Roeleveld <jo...@antarean.org>
Cc: Jürgen Groß <jgr...@suse.com>
---
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....@citrix.com>
+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
