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Re: [Qemu-devel] [PATCH v3] rcu: reduce more than 7MB heap memory by mal
From: |
Daniel P. Berrange |
Subject: |
Re: [Qemu-devel] [PATCH v3] rcu: reduce more than 7MB heap memory by malloc_trim() |
Date: |
Mon, 4 Dec 2017 12:07:05 +0000 |
User-agent: |
Mutt/1.9.1 (2017-09-22) |
On Mon, Dec 04, 2017 at 08:03:22PM +0800, Yang Zhong wrote:
> On Fri, Dec 01, 2017 at 01:52:49PM +0100, Paolo Bonzini wrote:
> > On 01/12/2017 11:56, Yang Zhong wrote:
> > > This issue should be caused by much times of system call by
> > > malloc_trim(),
> > > Shannon's test script include 60 scsi disks and 31 ioh3420 devices. We
> > > need
> > > trade-off between VM perforamance and memory optimization. Whether
> > > below
> > > method is suitable?
> > >
> > > int num=1;
> > > ......
> > >
> > > #if defined(CONFIG_MALLOC_TRIM)
> > > if(!(num++%5))
> > > {
> > > malloc_trim(4 * 1024 * 1024);
> > > }
> > > #endif
> > >
> > > Any comments are welcome! Thanks a lot!
> >
> > Indeed something like this will do, perhaps only trim once per second?
> >
> Hello Paolo,
>
> Thanks for comments!
> If we do trim once per second, maybe the frequency is a little high, what'e
> more, we need maintain one timer to call this, this also cost cpu resource.
>
> I added the log and did the test here with my test qemu command, when VM
> bootup,
> which did more than 600 times free operations and 9 times memory trim in
> rcu
> thread. If i use our ClearContainer qemu command, the memory trim will down
> to 6 times. As for Shannon's test command, the malloc trim number will
> abosultly
> increse.
>
> In my above method, the trim is only executed in the multiple of 5, which
> will
> reduce trim times and do not heavily impact VM bootup performance.
>
> I also want to use synchronize_rcu() and free() to replace call_rcu(), but
> this
> method serialize to malloc() and free(), which will reduce VM performance.
>
> The ultimate aim is to reduce trim system call during the VM bootup and
> running.
> It's appreciated that if you have better suggestions.
Does configuring QEMU to use tcmalloc or jemalloc instead of glibc's malloc
give you the performance & menmory usage that you require? If so, it might
not be worth bothering to hack around problems in glibc's malloc at all.
Regards,
Daniel
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- Re: [Qemu-devel] [PATCH v3] rcu: reduce more than 7MB heap memory by malloc_trim(), Yang Zhong, 2017/12/04
- Re: [Qemu-devel] [PATCH v3] rcu: reduce more than 7MB heap memory by malloc_trim(),
Daniel P. Berrange <=
- Re: [Qemu-devel] [PATCH v3] rcu: reduce more than 7MB heap memory by malloc_trim(), Shannon Zhao, 2017/12/04
- Re: [Qemu-devel] [PATCH v3] rcu: reduce more than 7MB heap memory by malloc_trim(), Yang Zhong, 2017/12/05
- Re: [Qemu-devel] [PATCH v3] rcu: reduce more than 7MB heap memory by malloc_trim(), Paolo Bonzini, 2017/12/05
- Re: [Qemu-devel] [PATCH v3] rcu: reduce more than 7MB heap memory by malloc_trim(), Yang Zhong, 2017/12/06
- Re: [Qemu-devel] [PATCH v3] rcu: reduce more than 7MB heap memory by malloc_trim(), Paolo Bonzini, 2017/12/06
- Re: [Qemu-devel] [PATCH v3] rcu: reduce more than 7MB heap memory by malloc_trim(), Yang Zhong, 2017/12/07
- Re: [Qemu-devel] [PATCH v3] rcu: reduce more than 7MB heap memory by malloc_trim(), Paolo Bonzini, 2017/12/11
- Re: [Qemu-devel] [PATCH v3] rcu: reduce more than 7MB heap memory by malloc_trim(), Yang Zhong, 2017/12/12