Patch name: dm-log-userspace-group-clear-and-mark-requests.patch
This patch allows the device-mapper log 'mark' and 'clear'
requests to be grouped and processed in a batch. This can
significantly reduce the amount of traffic going between
the kernel and userspace (where the processing daemon resides).
Signed-off-by: Jonathan Brassow <jbrassow@xxxxxxxxxx>
Index: linux-2.6/drivers/md/dm-log-userspace-base.c
===================================================================
--- linux-2.6.orig/drivers/md/dm-log-userspace-base.c
+++ linux-2.6/drivers/md/dm-log-userspace-base.c
@@ -17,6 +17,14 @@ struct flush_entry {
struct list_head list;
};
+/*
+ * This limit on the number of mark and clear request is, to a degree,
+ * arbitrary. However, there is some basis for the choice in the limits
+ * imposed on the size of data payload by dm-log-userspace-transfer.c:
+ * dm_consult_userspace().
+ */
+#define MAX_FLUSH_GROUP_COUNT 32
+
struct log_c {
struct dm_target *ti;
uint32_t region_size;
@@ -45,6 +53,7 @@ struct log_c {
spinlock_t flush_lock;
struct list_head mark_list;
struct list_head clear_list;
+ uint64_t group[MAX_FLUSH_GROUP_COUNT];
};
static mempool_t *flush_entry_pool;
@@ -348,6 +357,66 @@ static int userspace_in_sync(struct dm_d
return (r) ? 0 : (int)in_sync;
}
+static int flush_one_by_one(struct log_c *lc, struct list_head *flush_list)
+{
+ int r = 0;
+ struct flush_entry *fe;
+
+ list_for_each_entry(fe, flush_list, list) {
+ r = userspace_do_request(lc, lc->uuid, fe->type,
+ (char *)&fe->region,
+ sizeof(fe->region),
+ NULL, NULL);
+ if (r)
+ break;
+ }
+
+ return r;
+}
+
+static int flush_by_group(struct log_c *lc, struct list_head *flush_list)
+{
+ int r = 0;
+ int count;
+ uint32_t type;
+ struct flush_entry *fe, *tmp_fe;
+ LIST_HEAD(tmp_list);
+
+ /*
+ * Group process the requests
+ */
+ while (!list_empty(flush_list)) {
+ count = 0;
+
+ list_for_each_entry_safe(fe, tmp_fe, flush_list, list) {
+ lc->group[count] = fe->region;
+ count++;
+
+ list_del(&fe->list);
+ list_add(&fe->list, &tmp_list);
+
+ type = fe->type;
+ if (count >= MAX_FLUSH_GROUP_COUNT)
+ break;
+ }
+
+ r = userspace_do_request(lc, lc->uuid, type,
+ (char *)(lc->group),
+ count * sizeof(uint64_t),
+ NULL, NULL);
+ if (r) {
+ /* Group send failed. Attempt one-by-one. */
+ list_splice_init(&tmp_list, flush_list);
+ r = flush_one_by_one(lc, flush_list);
+ break;
+ }
+ }
+
+ list_splice_init(&tmp_list, flush_list);
+
+ return r;
+}
+
/*
* userspace_flush
*
@@ -382,30 +451,13 @@ static int userspace_flush(struct dm_dir
if (list_empty(&mark_list) && list_empty(&clear_list))
return 0;
- /*
- * FIXME: Count up requests, group request types,
- * allocate memory to stick all requests in and
- * send to server in one go. Failing the allocation,
- * do it one by one.
- */
-
- list_for_each_entry(fe, &mark_list, list) {
- r = userspace_do_request(lc, lc->uuid, fe->type,
- (char *)&fe->region,
- sizeof(fe->region),
- NULL, NULL);
- if (r)
- goto fail;
- }
+ r = flush_by_group(lc, &mark_list);
+ if (r)
+ goto fail;
- list_for_each_entry(fe, &clear_list, list) {
- r = userspace_do_request(lc, lc->uuid, fe->type,
- (char *)&fe->region,
- sizeof(fe->region),
- NULL, NULL);
- if (r)
- goto fail;
- }
+ r = flush_by_group(lc, &clear_list);
+ if (r)
+ goto fail;
r = userspace_do_request(lc, lc->uuid, DM_ULOG_FLUSH,
NULL, 0, NULL, NULL);
--
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