Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Subject: Re: [PATCH] dax: Fix missed PMD wakeups
To:     Matthew Wilcox <willy@infradead.org>
Cc:     Dan Williams <dan.j.williams@intel.com>,
        linux-fsdevel <linux-fsdevel@vger.kernel.org>,
        Jan Kara <jack@suse.cz>, stable <stable@vger.kernel.org>,
        Robert Barror <robert.barror@intel.com>,
        Seema Pandit <seema.pandit@intel.com>,
        linux-nvdimm <linux-nvdimm@lists.01.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
References: <156213869409.3910140.7715747316991468148.stgit@dwillia2-desk3.amr.corp.intel.com>
 <20190703121743.GH1729@bombadil.infradead.org>
 <CAPcyv4jgs5LTtTXR+2CyfbjJE85B_eoPFuXQsGBDnVMo41Jawg@mail.gmail.com>
 <20190703195302.GJ1729@bombadil.infradead.org>
 <CAPcyv4iPNz=oJyc_EoE-mC11=gyBzwMKbmj1ZY_Yna54=cC=Mg@mail.gmail.com>
 <20190704032728.GK1729@bombadil.infradead.org>
 <f23a1c71-d1b1-b279-c922-ce0f48cb4448@gmail.com>
 <20190704135804.GL1729@bombadil.infradead.org>
From:   Boaz Harrosh <openosd@gmail.com>
Message-ID: <bfe7c33d-7c3c-dcc0-5408-e23ea8223ef0@gmail.com>
Date:   Thu, 4 Jul 2019 17:32:23 +0300
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101
 Thunderbird/60.7.0
MIME-Version: 1.0
In-Reply-To: <20190704135804.GL1729@bombadil.infradead.org>
Content-Type: text/plain; charset=utf-8
Content-Language: en-MW
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On 04/07/2019 16:58, Matthew Wilcox wrote:
> On Thu, Jul 04, 2019 at 04:00:00PM +0300, Boaz Harrosh wrote:
<>
>> Matthew you must be kidding an ilog2 in binary is zero clocks
>> (Return the highest bit or something like that)
> 
> You might want to actually check the documentation instead of just
> making shit up.
> 

Yes you are right I stand corrected. Must be smoking ;-)

> https://www.agner.org/optimize/instruction_tables.pdf
> 
> I think in this instance what we want is BSR (aka ffz) since the input is
> going to be one of 0, 1, 3, 7, 15 or 31 (and we want 0, 1, 2, 3, 4, 5 as
> results).
> 
<>
> The compiler doesn't know the range of 'sibs'.  Unless we do the
> profile-feedback thing.
> 

Would you please consider the use of get_order() macro from #include <getorder.h>
Just for the sake of understanding? (Or at least a comment)

Thanks
Boaz