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authorYang Zhong <yang.zhong@intel.com>2017-12-20 21:16:46 +0800
committerPaolo Bonzini <pbonzini@redhat.com>2017-12-21 09:30:32 +0100
commit5a22ab71623c0fb709d49df353bdf2ec7c445c4c (patch)
tree291556c8f9de0574891260e025bbefe7f18baddd
parent6b012d2311e5ba0a952c2dcfe4327a73353c9fdb (diff)
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rcu: reduce more than 7MB heap memory by malloc_trim()
Since there are some issues in memory alloc/free machenism in glibc for little chunk memory, if Qemu frequently alloc/free little chunk memory, the glibc doesn't alloc little chunk memory from free list of glibc and still allocate from OS, which make the heap size bigger and bigger. This patch introduce malloc_trim(), which will free heap memory when there is no rcu call during rcu thread loop. malloc_trim() can be enabled/disabled by --enable-malloc-trim/ --disable-malloc-trim in the Qemu configure command. The default malloc_trim() is enabled for libc. Below are test results from smaps file. (1)without patch 55f0783e1000-55f07992a000 rw-p 00000000 00:00 0 [heap] Size: 21796 kB Rss: 14260 kB Pss: 14260 kB (2)with patch 55cc5fadf000-55cc61008000 rw-p 00000000 00:00 0 [heap] Size: 21668 kB Rss: 6940 kB Pss: 6940 kB Signed-off-by: Yang Zhong <yang.zhong@intel.com> Message-Id: <1513775806-19779-1-git-send-email-yang.zhong@intel.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
-rwxr-xr-xconfigure35
-rw-r--r--util/rcu.c6
2 files changed, 41 insertions, 0 deletions
diff --git a/configure b/configure
index 99ccc17..100309c 100755
--- a/configure
+++ b/configure
@@ -426,6 +426,7 @@ vxhs=""
supported_cpu="no"
supported_os="no"
bogus_os="no"
+malloc_trim=""
# parse CC options first
for opt do
@@ -1047,6 +1048,10 @@ for opt do
;;
--enable-tcg) tcg="yes"
;;
+ --disable-malloc-trim) malloc_trim="no"
+ ;;
+ --enable-malloc-trim) malloc_trim="yes"
+ ;;
--disable-spice) spice="no"
;;
--enable-spice) spice="yes"
@@ -1466,6 +1471,7 @@ Advanced options (experts only):
Default:trace-<pid>
--disable-slirp disable SLIRP userspace network connectivity
--enable-tcg-interpreter enable TCG with bytecode interpreter (TCI)
+ --enable-malloc-trim enable libc malloc_trim() for memory optimization
--oss-lib path to OSS library
--cpu=CPU Build for host CPU [$cpu]
--with-coroutine=BACKEND coroutine backend. Supported options:
@@ -3860,6 +3866,30 @@ if test "$tcmalloc" = "yes" && test "$jemalloc" = "yes" ; then
exit 1
fi
+# Even if malloc_trim() is available, these non-libc memory allocators
+# do not support it.
+if test "$tcmalloc" = "yes" || test "$jemalloc" = "yes" ; then
+ if test "$malloc_trim" = "yes" ; then
+ echo "Disabling malloc_trim with non-libc memory allocator"
+ fi
+ malloc_trim="no"
+fi
+
+#######################################
+# malloc_trim
+
+if test "$malloc_trim" != "no" ; then
+ cat > $TMPC << EOF
+#include <malloc.h>
+int main(void) { malloc_trim(0); return 0; }
+EOF
+ if compile_prog "" "" ; then
+ malloc_trim="yes"
+ else
+ malloc_trim="no"
+ fi
+fi
+
##########################################
# tcmalloc probe
@@ -5505,6 +5535,7 @@ if test "$tcg" = "yes" ; then
echo "TCG debug enabled $debug_tcg"
echo "TCG interpreter $tcg_interpreter"
fi
+echo "malloc trim support $malloc_trim"
echo "RDMA support $rdma"
echo "fdt support $fdt"
echo "preadv support $preadv"
@@ -6015,6 +6046,10 @@ if test "$opengl" = "yes" ; then
fi
fi
+if test "$malloc_trim" = "yes" ; then
+ echo "CONFIG_MALLOC_TRIM=y" >> $config_host_mak
+fi
+
if test "$avx2_opt" = "yes" ; then
echo "CONFIG_AVX2_OPT=y" >> $config_host_mak
fi
diff --git a/util/rcu.c b/util/rcu.c
index ca5a63e..f4d09c8 100644
--- a/util/rcu.c
+++ b/util/rcu.c
@@ -32,6 +32,9 @@
#include "qemu/atomic.h"
#include "qemu/thread.h"
#include "qemu/main-loop.h"
+#if defined(CONFIG_MALLOC_TRIM)
+#include <malloc.h>
+#endif
/*
* Global grace period counter. Bit 0 is always one in rcu_gp_ctr.
@@ -246,6 +249,9 @@ static void *call_rcu_thread(void *opaque)
qemu_event_reset(&rcu_call_ready_event);
n = atomic_read(&rcu_call_count);
if (n == 0) {
+#if defined(CONFIG_MALLOC_TRIM)
+ malloc_trim(4 * 1024 * 1024);
+#endif
qemu_event_wait(&rcu_call_ready_event);
}
}