Add rbdcache max dirty object option

Librbd will calculate max dirty object according to rbd_cache_max_size, it
doesn't suitable for every case. If user set image order 24, the calculating
result is too small for reality. It will increase the overhead of trim call
which is called each read/write op.

Now we make it as option for tunning, by default this value is calculated.

Signed-off-by: Haomai Wang <haomaiwang@gmail.com>

diff --git a/src/common/config_opts.h b/src/common/config_opts.h
index 823634bf268bc4bccc0700be3a1e74803f9b5492..0fbe8d03364db498c97ba940bdc395ea09a1e712 100644 (file)
--- a/src/common/config_opts.h
+++ b/src/common/config_opts.h
@@ -728,6 +728,7 @@ OPTION(rbd_cache_size, OPT_LONGLONG, 32<<20)         // cache size in bytes
 OPTION(rbd_cache_max_dirty, OPT_LONGLONG, 24<<20)    // dirty limit in bytes - set to 0 for write-through caching
 OPTION(rbd_cache_target_dirty, OPT_LONGLONG, 16<<20) // target dirty limit in bytes
 OPTION(rbd_cache_max_dirty_age, OPT_FLOAT, 1.0)      // seconds in cache before writeback starts
+OPTION(rbd_cache_max_dirty_object, OPT_INT, 0)       // dirty limit for objects - set to 0 for auto calculate from rbd_cache_size
 OPTION(rbd_cache_block_writes_upfront, OPT_BOOL, false) // whether to block writes to the cache before the aio_write call completes (true), or block before the aio completion is called (false)
 OPTION(rbd_concurrent_management_ops, OPT_INT, 10) // how many operations can be in flight for a management operation like deleting or resizing an image
 OPTION(rbd_balance_snap_reads, OPT_BOOL, false)

diff --git a/src/librbd/ImageCtx.cc b/src/librbd/ImageCtx.cc
index d2f0a4a96b19377cbfe70900225f2540cf7d1811..b5c2db6e7895ee9205f084e73bfbd80399929f8b 100644 (file)
--- a/src/librbd/ImageCtx.cc
+++ b/src/librbd/ImageCtx.cc
@@ -185,10 +185,14 @@ namespace librbd {
 
     // size object cache appropriately
     if (object_cacher) {
-      uint64_t obj = cct->_conf->rbd_cache_size / (1ull << order);
+      uint64_t obj = cct->_conf->rbd_cache_max_dirty_object;
+      if (!obj) {
+        obj = cct->_conf->rbd_cache_size / (1ull << order);
+        obj = obj * 4 + 10;
+      }
       ldout(cct, 10) << " cache bytes " << cct->_conf->rbd_cache_size << " order " << (int)order
                     << " -> about " << obj << " objects" << dendl;
-      object_cacher->set_max_objects(obj * 4 + 10);
+      object_cacher->set_max_objects(obj);
     }
 
     ldout(cct, 10) << "init_layout stripe_unit " << stripe_unit
@@ -587,7 +591,7 @@ namespace librbd {
     cache_lock.Unlock();
     if (unclean) {
       lderr(cct) << "could not release all objects from cache: "
-                << unclean << " bytes remain" << dendl;
+                 << unclean << " bytes remain" << dendl;
       return -EBUSY;
     }
     return r;