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Re: [Qemu-devel] [PATCH v2] rcu: reduce more than 7MB heap memory by mal
From: |
Zhong Yang |
Subject: |
Re: [Qemu-devel] [PATCH v2] rcu: reduce more than 7MB heap memory by malloc_trim() |
Date: |
Fri, 24 Nov 2017 14:29:07 +0800 |
User-agent: |
Mutt/1.5.21 (2010-09-15) |
On Thu, Nov 23, 2017 at 11:19:43AM +0000, Stefan Hajnoczi wrote:
> On Thu, Nov 23, 2017 at 02:41:16PM +0800, 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 | 4 ++++
> > util/rcu.c | 6 ++++++
> > 2 files changed, 10 insertions(+)
> >
> > diff --git a/configure b/configure
> > index 0e856bb..5b463d4 100755
> > --- a/configure
> > +++ b/configure
> > @@ -6012,6 +6012,10 @@ if test "$opengl" = "yes" ; then
> > fi
> > fi
> >
> > +if test "$tcmalloc" = "yes" || test "$jemalloc" = "yes" ; then
> > + echo "CONFIG_NONGLIBMALLOC=y" >> $config_host_mak
>
> malloc(3) is provided by glibc, not glib, so the name
> CONFIG_NONGLIBMALLOC is confusing.
>
> I suggest calling it CONFIG_MALLOC_TRIM instead:
>
> # Even if malloc_trim() is available, these non-libc memory allocators
> # do not support it.
> if test "$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
>
> if test "$malloc_trim" != "no" ; then
> cat > $TMPC << EOF
> #include <malloc.h>
> int main(void) { malloc_trim(0); return 0; }
> EOF
> if compile_prog "" "" ; then
> malloc_trim="yes"
> else
> malloc_trim="no"
> fi
> fi
>
> ...
>
> if test "$malloc_trim" = "yes" ; then
> echo "CONFIG_MALLOC_TRIM=y" >> $config_host_mak
> fi
>
> Then the code in rcu.c just has to #ifdef CONFIG_MALLOC_TRIM and there's
> no need for Linux-specific checks. If other operating systems support
> malloc_trim() then QEMU will use it by default.
Hello Stefan,
Thanks for your detailed infomation!
I did test with this new patch, which are okay, thanks again!
I will send V3 patch soon, please help review again! thanks!
Regards,
Yang