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Date: Thu, 11 Aug 2016 11:13:47 +0200
From: Ingo Molnar <mingo@kernel.org>
To: Aaron Lu <aaron.lu@intel.com>
Cc: x86@kernel.org, linux-kernel@vger.kernel.org,
        Alex Shi <alex.shi@linaro.org>,
        Tomoki Sekiyama <tomoki.sekiyama.qu@hitachi.com>,
        Davidlohr Bueso <dave@stgolabs.net>, Huang Ying <ying.huang@intel.com>,
        Ingo Molnar <mingo@redhat.com>, Thomas Gleixner <tglx@linutronix.de>,
        "\"H. Peter Anvin\"" <hpa@zytor.com>
Subject: Re: [PATCH] x86/irq: do not substract irq_tlb_count from
 irq_call_count
Message-ID: <20160811091347.GA10990@gmail.com>
References: <20160811074430.GA18163@aaronlu.sh.intel.com>
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* Aaron Lu <aaron.lu@intel.com> wrote:

> This is found by LKP's cyclic performance regression tracking recently
> with the vm-scalability test suite. I have bisected to commit
> 0a7ce4b5a632 ("mm/rmap: share the i_mmap_rwsem"). This commit didn't do
> anything wrong but revealed the irq_call_count problem. IIUC, the commit
> makes rwc->remap_one in rmap_walk_file concurrent with multiple threads.
> When remap_one is try_to_unmap_one, then multiple threads could queue
> flush tlb to the same CPU but only one IPI will be sent.

Note, for some reason the commit ID you used is wrong, the real one is:

  3dec0ba0be6a ("mm/rmap: share the i_mmap_rwsem")

I have fixed this in the changelog.

Thanks,

	Ingo