Date: Tue, 8 Oct 2013 16:17:00 +0900
From: Minchan Kim <minchan@kernel.org>
To: KOSAKI Motohiro <kosaki.motohiro@gmail.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>, John Stultz <john.stultz@linaro.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Android Kernel Team <kernel-team@android.com>,
        Robert Love <rlove@google.com>, Mel Gorman <mel@csn.ul.ie>,
        Hugh Dickins <hughd@google.com>, Dave Hansen <dave.hansen@intel.com>,
        Rik van Riel <riel@redhat.com>,
        Dmitry Adamushko <dmitry.adamushko@gmail.com>,
        Dave Chinner <david@fromorbit.com>, Neil Brown <neilb@suse.de>,
        Andrea Righi <andrea@betterlinux.com>,
        Andrea Arcangeli <aarcange@redhat.com>,
        "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>,
        Mike Hommey <mh@glandium.org>, Taras Glek <tglek@mozilla.com>,
        Dhaval Giani <dhaval.giani@gmail.com>, Jan Kara <jack@suse.cz>,
        Michel Lespinasse <walken@google.com>, Rob Clark <robdclark@gmail.com>,
        "linux-mm@kvack.org" <linux-mm@kvack.org>
Subject: Re: [PATCH 05/14] vrange: Add new vrange(2) system call
Message-ID: <20131008071700.GC29509@bbox>
References: <525347BE.7040606@zytor.com>
 <525349AE.1070904@linaro.org>
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 <20131008001306.GD25780@bbox>
 <52535EE1.3060700@zytor.com>
 <20131008020847.GH25780@bbox>
 <52537326.7000505@gmail.com>
 <20131008030736.GA29509@bbox>
 <52538B95.6080208@gmail.com>
 <20131008071202.GB29509@bbox>
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On Tue, Oct 08, 2013 at 04:12:02PM +0900, Minchan Kim wrote:
> On Tue, Oct 08, 2013 at 12:35:33AM -0400, KOSAKI Motohiro wrote:
> > (10/7/13 11:07 PM), Minchan Kim wrote:
> > >Hi KOSAKI,
> > >
> > >On Mon, Oct 07, 2013 at 10:51:18PM -0400, KOSAKI Motohiro wrote:
> > >>>Maybe, int madvise5(addr, length, MADV_DONTNEED|MADV_LAZY|MADV_SIGBUS,
> > >>>         &purged, &ret);
> > >>>
> > >>>Another reason to make it hard is that madvise(2) is tight coupled with
> > >>>with vmas split/merge. It needs mmap_sem's write-side lock and it hurt
> > >>>anon-vrange test performance much heavily and userland might want to
> > >>>make volatile range with small unit like "page size" so it's undesireable
> > >>>to make it with vma. Then, we should filter out to avoid vma split/merge
> > >>>in implementation if only MADV_LAZY case? Doable but it could make code
> > >>>complicated and lost consistency with other variant of madvise.
> > >>
> > >>I haven't seen your performance test result. Could please point out URLs?
> > >
> > >https://lkml.org/lkml/2013/3/12/105
> > 
> > It's not comparison with and without vma merge. I'm interest how much benefit
> > vmas operation avoiding have.
> 
> I had an number but lost it so I should set up it in my KVM machine :(
> And I needed old kernel 3.7.0 for testing vma-based approach.
> 
> DRAM:2G, CPU : 12 
> 
> kernel 3.7.0
> 
> jemalloc: 20527 records/s
> jemalloc vma based approach : 5360 records/s
> 
> vrange call made worse because every thread stuck with mmap_sem.
> 
> kernel 3.11.0
> 
> jemalloc: 21176 records/s
> jemalloc vroot tree approach: 103637 records/s
> 
> It could enhance 5 times.

And please keep in mind that vrange's user might want to small vrange
like PAGE_SIZE. If we go with vma-based approach, we would consume memory
with lots of vm_area_struct.

-- 
Kind regards,
Minchan Kim
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