Re: [RFC v2] Support volatile range for anon vma

[Arun Sharma]

On Wed, Oct 31, 2012 at 06:56:05PM -0400, KOSAKI Motohiro wrote:
> glibc malloc discard freed memory by using MADV_DONTNEED
> as tcmalloc. and it is often a source of large performance decrease.
> because of MADV_DONTNEED discard memory immediately and
> right after malloc() call fall into page fault and pagesize memset() path.
> then, using DONTNEED increased zero fill and cache miss rate.

The memcg based solution that I posted a few months ago is working well
for us. We see significantly less cpu in zero'ing pages.

Not everyone was comfortable with the security implications of recycling
pages between processes in a memcg, although it was disabled by default
and had to be explicitly opted-in.

Also, memory allocators have a second motivation in using madvise: to
create virtually contiguous regions of memory from a fragmented address 
space, without increasing the RSS.

 -Arun
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