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

[Alexandre DERUMIER]

Hi Paolo,

>>What is the peak memory usage of jemalloc and tcmalloc?

I'll try to use an heap profiling to see.
Don't known if "perf" can give me the info easily without profiling ?



----- Mail original -----
De: "pbonzini" <address@hidden>
À: "aderumier" <address@hidden>, "qemu-devel" <address@hidden>
Envoyé: Mardi 23 Juin 2015 09:57:19
Objet: Re: [PATCH] configure: Add support for jemalloc

On 19/06/2015 12:56, Alexandre Derumier wrote: 
> 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 

It's also possible to do 

MallocExtension_SetNumericProperty("tcmalloc.max_total_thread_cache_bytes", 
num_io_threads << 24); 

What is the peak memory usage of jemalloc and tcmalloc? 

Paolo 

> 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" 
>