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From:   Dan Williams <dan.j.williams@intel.com>
Date:   Mon, 17 Jun 2019 23:44:34 -0700
Message-ID: <CAPcyv4hpWg5DWRhazS-ftyghiZP-J_M-7Vd5tiUd5UKONOib8g@mail.gmail.com>
Subject: Re: [PATCH 0/3] resource: find_next_iomem_res() improvements
To:     Nadav Amit <namit@vmware.com>
Cc:     Andrew Morton <akpm@linux-foundation.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Linux MM <linux-mm@kvack.org>, Borislav Petkov <bp@suse.de>,
        Toshi Kani <toshi.kani@hpe.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        Bjorn Helgaas <bhelgaas@google.com>,
        Ingo Molnar <mingo@kernel.org>
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On Wed, Jun 12, 2019 at 9:59 PM Nadav Amit <namit@vmware.com> wrote:
>
> Running some microbenchmarks on dax keeps showing find_next_iomem_res()
> as a place in which significant amount of time is spent. It appears that
> in order to determine the cacheability that is required for the PTE,
> lookup_memtype() is called, and this one traverses the resources list in
> an inefficient manner. This patch-set tries to improve this situation.

Let's just do this lookup once per device, cache that, and replay it
to modified vmf_insert_* routines that trust the caller to already
know the pgprot_values.