Commit 5a22ab71 authored by Yang Zhong's avatar Yang Zhong Committed by Paolo Bonzini
Browse files

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: default avatarYang Zhong <yang.zhong@intel.com>
Message-Id: <1513775806-19779-1-git-send-email-yang.zhong@intel.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 6b012d23

configure

+35 −0
Original line number Diff line number Diff line
@@ -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

util/rcu.c

+6 −0
Original line number Diff line number Diff line
@@ -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);

                }

            }