linux-kernel - Re: [RFC 0/4]x86: allocate up to 32 tlb invalidate vectors

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Message-ID: <1289829765.14740.2.camel@sli10-conroe>
Date:	Mon, 15 Nov 2010 22:02:45 +0800
From:	Shaohua Li <shaohua.li@...el.com>
To:	lkml <linux-kernel@...r.kernel.org>
Cc:	Ingo Molnar <mingo@...e.hu>, Andi Kleen <andi@...stfloor.org>,
	"hpa@...or.com" <hpa@...or.com>
Subject: Re: [RFC 0/4]x86: allocate up to 32 tlb invalidate vectors

On Wed, 2010-11-03 at 14:44 +0800, Shaohua Li wrote:
> 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.
> 
Hi Ingo & hpa, any comments about this series?

Thanks,
Shaohua

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