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Re: [Qemu-devel] [PATCH v3] rcu: reduce more than 7MB heap memory by mal
From: |
Shannon Zhao |
Subject: |
Re: [Qemu-devel] [PATCH v3] rcu: reduce more than 7MB heap memory by malloc_trim() |
Date: |
Sun, 26 Nov 2017 14:17:18 +0800 |
User-agent: |
Mozilla/5.0 (Windows NT 6.1; rv:24.0) Gecko/20100101 Thunderbird/24.4.0 |
Hi,
On 2017/11/24 14:30, Yang Zhong wrote:
> 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.
>
> 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 <address@hidden>
> ---
> configure | 29 +++++++++++++++++++++++++++++
> util/rcu.c | 6 ++++++
> 2 files changed, 35 insertions(+)
>
> diff --git a/configure b/configure
> index 0c6e757..6292ab0 100755
> --- a/configure
> +++ b/configure
> @@ -426,6 +426,7 @@ vxhs=""
> supported_cpu="no"
> supported_os="no"
> bogus_os="no"
> +malloc_trim="yes"
>
> # parse CC options first
> for opt do
> @@ -3857,6 +3858,30 @@ 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 > $TMPC << EOF
> +#include <malloc.h>
> +int main(void) { malloc_trim(0); return 0; }
> +EOF
> + if compile_prog "" "" ; then
> + malloc_trim="yes"
> + else
> + malloc_trim="no"
> + fi
> +fi
> +
> ##########################################
> # tcmalloc probe
>
> @@ -6012,6 +6037,10 @@ if test "$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..f403b77 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.
> @@ -272,6 +275,9 @@ static void *call_rcu_thread(void *opaque)
> node->func(node);
> }
> qemu_mutex_unlock_iothread();
> +#if defined(CONFIG_MALLOC_TRIM)
> + malloc_trim(4 * 1024 * 1024);
> +#endif
> }
> abort();
> }
>
Looks like this patch introduces a performance regression. With this
patch the time of booting a VM with 60 scsi disks on ARM64 is increased
by 200+ seconds.
Thanks,
--
Shannon