Re: [Qemu-devel] [PATCH v4] rcu: reduce more than 7MB heap memory by malloc_trim()

[Stefan Hajnoczi <stefanha@redhat.com>]

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On Wed, Dec 20, 2017 at 09:16:46PM +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 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>
> ---
>  configure  | 35 +++++++++++++++++++++++++++++++++++
>  util/rcu.c |  6 ++++++
>  2 files changed, 41 insertions(+)

Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>

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