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List:       ceph-devel
Subject:    [ceph-devel] [cppcheck] suggested a few performance improvements
From:       "Martin Ettl" <ettl.martin () gmx ! de>
Date:       2010-03-22 20:35:02
Message-ID: 20100322203502.295370 () gmx ! net
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Hello,

i have checked the current git head with cppcheck ( a static code analysis tool, \
http://sourceforge.net/projects/cppcheck/). It is an allready very powerfull tool \
that makes some suggestions, how to improve performance of the code.

Here is a snipped of the scan:
....
[./src/mds/MDSMap.h:236]: (possible style) Pre-Incrementing variable 'p' is preferred \
to Post-Incrementing [./src/mds/MDSMap.h:256]: (possible style) Pre-Incrementing \
variable 'p' is preferred to Post-Incrementing [./src/mds/MDSMap.h:263]: (possible \
style) Pre-Incrementing variable 'p' is preferred to Post-Incrementing \
[./src/mds/MDSMap.h:280]: (possible style) Pre-Incrementing variable 'p' is preferred \
to Post-Incrementing [./src/mds/MDSMap.h:291]: (possible style) Pre-Incrementing \
variable 'p' is preferred to Post-Incrementing [./src/include/LogEntry.h:100]: \
(possible style) Pre-Incrementing variable 'p' is preferred to Post-Incrementing \
[./src/ceph.cc:317]: (possible style) Pre-Incrementing variable 'p' is preferred to \
Post-Incrementing [./src/mds/MDSMap.h:247]: (possible style) Use failed.empty() \
                instead of failed.size() to guarantee fast code.
....


Please refer the attached patch that chanes a few of this suggestions.
What do you think about this? Does it boost the performance?

Best regards

Ettl Martin

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["Performance_improvements_cppcheck.patch" (text/x-patch)]

diff --git a/src/mds/Capability.h b/src/mds/Capability.h
index 6afbe98..571e50e 100644
--- a/src/mds/Capability.h
+++ b/src/mds/Capability.h
@@ -183,7 +183,7 @@ public:
   }
   void _calc_issued() {
     _issued = _pending;
-    for (list<revoke_info>::iterator p = _revokes.begin(); p != _revokes.end(); p++)
+    for (list<revoke_info>::iterator p = _revokes.begin(); p != _revokes.end(); ++p)
       _issued |= p->before;
   }
   void confirm_receipt(ceph_seq_t seq, unsigned caps) {
diff --git a/src/mds/MDSMap.h b/src/mds/MDSMap.h
index 533ec4f..2def085 100644
--- a/src/mds/MDSMap.h
+++ b/src/mds/MDSMap.h
@@ -220,7 +220,7 @@ public:
     unsigned n = 0;
     for (map<__u64,mds_info_t>::const_iterator p = mds_info.begin();
 	 p != mds_info.end();
-	 p++)
+	 ++p)
       if (p->second.state == state) ++n;
     return n;
   }
@@ -234,7 +234,7 @@ public:
   void get_up_mds_set(set<int>& s) {
     for (map<int32_t,__u64>::const_iterator p = up.begin();
 	 p != up.end();
-	 p++)
+	 ++p)
       s.insert(p->first);
   }
   void get_active_mds_set(set<int>& s) {
@@ -244,7 +244,7 @@ public:
     s = failed;
   }
   int get_failed() {
-    if (failed.size()) return *failed.begin();
+    if (!failed.empty()) return *failed.begin();
     return -1;
   }
   void get_stopped_mds_set(set<int>& s) {
@@ -254,14 +254,14 @@ public:
     s = failed;
     for (map<__u64,mds_info_t>::const_iterator p = mds_info.begin();
 	 p != mds_info.end();
-	 p++)
+	 ++p)
       if (p->second.state >= STATE_REPLAY && p->second.state <= STATE_STOPPING)
 	s.insert(p->second.rank);
   }
   void get_mds_set(set<int>& s, int state) {
     for (map<__u64,mds_info_t>::const_iterator p = mds_info.begin();
 	 p != mds_info.end();
-	 p++)
+	 ++p)
       if (p->second.state == state)
 	s.insert(p->second.rank);
   } 
@@ -278,7 +278,7 @@ public:
   __u64 find_standby_for(int mds, string& name) {
     for (map<__u64,mds_info_t>::const_iterator p = mds_info.begin();
 	 p != mds_info.end();
-	 p++) {
+	 ++p) {
       if (p->second.rank == -1 &&
 	  (p->second.standby_for_rank == mds ||
 	   p->second.standby_for_name == name) &&
@@ -289,7 +289,7 @@ public:
     }
     for (map<__u64,mds_info_t>::const_iterator p = mds_info.begin();
 	 p != mds_info.end();
-	 p++) {
+	 ++p) {
       if (p->second.rank == -1 &&
 	  p->second.standby_for_rank < 0 &&
 	  p->second.standby_for_name.length() == 0 &&
diff --git a/src/mds/mdstypes.h b/src/mds/mdstypes.h
index ca8b9ae..465defc 100644
--- a/src/mds/mdstypes.h
+++ b/src/mds/mdstypes.h
@@ -385,7 +385,7 @@ struct inode_t {
     __u64 max = 0;
       for (map<client_t,byte_range_t>::const_iterator p = client_ranges.begin();
 	   p != client_ranges.end();
-	   p++)
+	   ++p)
 	if (p->second.last > max)
 	  max = p->second.last;
       return max;
@@ -396,7 +396,7 @@ struct inode_t {
     } else {
       for (map<client_t,byte_range_t>::iterator p = client_ranges.begin();
 	   p != client_ranges.end();
-	   p++)
+	   ++p)
 	p->second.last = new_max;
     }
   }
@@ -1331,7 +1331,7 @@ protected:
     }
     for (multimap<__u64,Context*>::iterator p = waiting.lower_bound(min);
 	 p != waiting.end();
-	 p++) {
+	 ++p) {
       if (p->first & mask) return true;
       if (p->first > mask) return false;
     }


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