dm log userspace: group clear and mark requests

Allow the device-mapper log's '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@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>

1 files changed, 79 insertions, 23 deletions

diff --git a/drivers/md/dm-log-userspace-base.c b/drivers/md/dm-log-userspace-base.c
index 767adf300fa5..31e1687e7bf6 100644
--- a/drivers/md/dm-log-userspace-base.c
+++ b/drivers/md/dm-log-userspace-base.c
@@ -18,6 +18,14 @@ 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;
@@ -348,6 +356,71 @@ static int userspace_in_sync(struct dm_dirty_log *log, region_t region,
         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 = 0;
+        struct flush_entry *fe, *tmp_fe;
+        LIST_HEAD(tmp_list);
+        uint64_t group[MAX_FLUSH_GROUP_COUNT];
+
+        /*
+         * Group process the requests
+         */
+        while (!list_empty(flush_list)) {
+                count = 0;
+
+                list_for_each_entry_safe(fe, tmp_fe, flush_list, list) {
+                        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 *)(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;
+                }
+        }
+
+        /*
+         * Must collect flush_entrys that were successfully processed
+         * as a group so that they will be free'd by the caller.
+         */
+        list_splice_init(&tmp_list, flush_list);
+
+        return r;
+}
+
 /*
  * userspace_flush
  *
@@ -382,30 +455,13 @@ static int userspace_flush(struct dm_dirty_log *log)
         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);