[Qemu-devel] [PATCH] configure: Add support for jemalloc

[Alexandre Derumier]

This adds "--enable-jemalloc" and "--disable-jemalloc" to allow linking
to jemalloc memory allocator.

We have already tcmalloc support,
but it seem to not working well with a lot of iothreads/disks.

The main problem is that tcmalloc use a shared thread cache of 16MB
by default.
With more threads, this cache is shared, and some bad garbage collections
can occur if the cache is too low.

It's possible to tcmalloc cache increase it with a env var:
TCMALLOC_MAX_TOTAL_THREAD_CACHE_BYTES=256MB

With default 16MB, performances are  really bad with more than 2 disks.
Increasing to 256MB, it's helping but still have problem with 16 
disks/iothreads.

Jemalloc don't have performance problem with default configuration.

Here the benchmark results in iops of 1 qemu vm randread 4K iodepth=32,
with rbd block backend (librbd is doing a lot of memory allocation),
1 iothread by disk

glibc malloc
------------

1 disk      29052
2 disks     55878
4 disks     127899
8 disks     240566
15 disks    269976

jemalloc
--------

1 disk      41278
2 disks     75781
4 disks     195351
8 disks     294241
15 disks    298199

tcmalloc 2.2.1 default 16M cache
--------------------------------

1 disk   37911
2 disks  67698
4 disks  41076
8 disks  43312
15 disks 37569

tcmalloc : 256M cache
---------------------------

1 disk     33914
2 disks    58839
4 disks    148205
8 disks    213298
15 disks   218383

Signed-off-by: Alexandre Derumier <address@hidden>
---
 configure | 29 +++++++++++++++++++++++++++++
 1 file changed, 29 insertions(+)

diff --git a/configure b/configure
index 222694f..2fe1e05 100755
--- a/configure
+++ b/configure
@@ -336,6 +336,7 @@ vhdx=""
 quorum=""
 numa=""
 tcmalloc="no"
+jemalloc="no"
 
 # parse CC options first
 for opt do
@@ -1147,6 +1148,10 @@ for opt do
   ;;
   --enable-tcmalloc) tcmalloc="yes"
   ;;
+  --disable-jemalloc) jemalloc="no"
+  ;;
+  --enable-jemalloc) jemalloc="yes"
+  ;;
   *)
       echo "ERROR: unknown option $opt"
       echo "Try '$0 --help' for more information"
@@ -1420,6 +1425,8 @@ Advanced options (experts only):
   --enable-numa            enable libnuma support
   --disable-tcmalloc       disable tcmalloc support
   --enable-tcmalloc        enable tcmalloc support
+  --disable-jemalloc       disable jemalloc support
+  --enable-jemalloc        enable jemalloc support
 
 NOTE: The object files are built at the place where configure is launched
 EOF
@@ -3344,6 +3351,11 @@ EOF
   fi
 fi
 
+if test "$tcmalloc" = "yes" && test "$jemalloc" = "yes" ; then
+    echo "ERROR: tcmalloc && jemalloc can't be used at the same time"
+    exit 1
+fi
+
 ##########################################
 # tcmalloc probe
 
@@ -3361,6 +3373,22 @@ EOF
 fi
 
 ##########################################
+# jemalloc probe
+
+if test "$jemalloc" = "yes" ; then
+  cat > $TMPC << EOF
+#include <stdlib.h>
+int main(void) { malloc(1); return 0; }
+EOF
+
+  if compile_prog "" "-ljemalloc" ; then
+    LIBS="-ljemalloc $LIBS"
+  else
+    feature_not_found "jemalloc" "install jemalloc devel"
+  fi
+fi
+
+##########################################
 # signalfd probe
 signalfd="no"
 cat > $TMPC << EOF
@@ -4499,6 +4527,7 @@ echo "snappy support    $snappy"
 echo "bzip2 support     $bzip2"
 echo "NUMA host support $numa"
 echo "tcmalloc support  $tcmalloc"
+echo "jemalloc support  $jemalloc"
 
 if test "$sdl_too_old" = "yes"; then
 echo "-> Your SDL version is too old - please upgrade to have SDL support"
-- 
2.1.4