Subject: Re: [PATCH 0/4]x86: allocate up to 32 tlb invalidate vectors
 -resend
From: Shaohua Li <shaohua.li@intel.com>
To: lkml <linux-kernel@vger.kernel.org>
Cc: Ingo Molnar <mingo@elte.hu>, Andi Kleen <andi@firstfloor.org>,
        "hpa@zytor.com" <hpa@zytor.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Eric Dumazet <eric.dumazet@gmail.com>
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References: <1295232719.1949.706.camel@sli10-conroe>
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Date: Mon, 14 Feb 2011 10:38:18 +0800
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On Mon, 2011-01-17 at 10:51 +0800, Shaohua Li wrote:
> last post is lost, resent.
> 
> Hi,
> In workload with heavy page reclaim, flush_tlb_page() is frequently
> used. We currently have 8 vectors for tlb flush, which is fine for small
> machines. But for big machines with a lot of CPUs, the 8 vectors are
> shared by all CPUs and we need lock to protect them. This will cause a
> lot of lock contentions. please see the patch 3 for detailed number of
> the lock contention.
> Andi Kleen suggests we can use 32 vectors for tlb flush, which should be
> fine for even 8 socket machines. Test shows this reduces lock contention
> dramatically (see patch 3 for number).
> One might argue if this will waste too many vectors and leave less
> vectors for devices. This could be a problem. But even we use 32
> vectors, we still leave 78 vectors for devices. And we now have per-cpu
> vector, vector isn't scarce any more, but I'm open if anybody has
> objections.
any comments on this patch set?

Thanks,
Shaohua


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