From: "Roedel, Joerg" <Joerg.Roedel@amd.com>
To: Ohad Ben-Cohen <ohad@wizery.com>
Cc: "iommu@lists.linux-foundation.org"
<iommu@lists.linux-foundation.org>,
"linux-omap@vger.kernel.org" <linux-omap@vger.kernel.org>,
Hiroshi DOYU <Hiroshi.DOYU@nokia.com>,
Laurent Pinchart <laurent.pinchart@ideasonboard.com>,
David Woodhouse <dwmw2@infradead.org>,
"linux-arm-kernel@lists.infradead.org"
<linux-arm-kernel@lists.infradead.org>,
David Brown <davidb@codeaurora.org>,
Arnd Bergmann <arnd@arndb.de>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Stepan Moskovchenko <stepanm@codeaurora.org>,
"kvm@vger.kernel.org" <kvm@vger.kernel.org>
Subject: Re: [PATCH v3 1/6] iommu/core: split mapping to page sizes as supported by the hardware
Date: Tue, 27 Sep 2011 15:12:22 +0200 [thread overview]
Message-ID: <20110927131222.GL2138@amd.com> (raw)
In-Reply-To: <CAK=WgbahwY+7Ux-RjW2Tw9WBSwZnYuTMZ2NQASWyOXQ3zF6qFg@mail.gmail.com>
On Tue, Sep 27, 2011 at 08:26:29AM -0400, Ohad Ben-Cohen wrote:
> > With an unsigned long you can use plain and fast bit_ops instead of the
> > full bitmap functions.
>
> Not sure I follow; the only bit operation I'm using while mapping is
> find_next_bit() (which is a bitops.h method).
>
> What other faster variant are you referring to ?
You pass a pointer to an unsigned long for the page-size bitmap. This
allows to use an array of unsigned long. But a single unsigned long is
sufficient and you can use functions like ffs() and fls() together with
shifting. These functions often translate to a single intruction in the
binary. The find_next_bit function has much more overhead because it
needs to handle the array-of-ulong case.
Joerg
--
AMD Operating System Research Center
Advanced Micro Devices GmbH Einsteinring 24 85609 Dornach
General Managers: Alberto Bozzo, Andrew Bowd
Registration: Dornach, Landkr. Muenchen; Registerger. Muenchen, HRB Nr. 43632
WARNING: multiple messages have this Message-ID (diff)
From: Joerg.Roedel@amd.com (Roedel, Joerg)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH v3 1/6] iommu/core: split mapping to page sizes as supported by the hardware
Date: Tue, 27 Sep 2011 15:12:22 +0200 [thread overview]
Message-ID: <20110927131222.GL2138@amd.com> (raw)
In-Reply-To: <CAK=WgbahwY+7Ux-RjW2Tw9WBSwZnYuTMZ2NQASWyOXQ3zF6qFg@mail.gmail.com>
On Tue, Sep 27, 2011 at 08:26:29AM -0400, Ohad Ben-Cohen wrote:
> > With an unsigned long you can use plain and fast bit_ops instead of the
> > full bitmap functions.
>
> Not sure I follow; the only bit operation I'm using while mapping is
> find_next_bit() (which is a bitops.h method).
>
> What other faster variant are you referring to ?
You pass a pointer to an unsigned long for the page-size bitmap. This
allows to use an array of unsigned long. But a single unsigned long is
sufficient and you can use functions like ffs() and fls() together with
shifting. These functions often translate to a single intruction in the
binary. The find_next_bit function has much more overhead because it
needs to handle the array-of-ulong case.
Joerg
--
AMD Operating System Research Center
Advanced Micro Devices GmbH Einsteinring 24 85609 Dornach
General Managers: Alberto Bozzo, Andrew Bowd
Registration: Dornach, Landkr. Muenchen; Registerger. Muenchen, HRB Nr. 43632
next prev parent reply other threads:[~2011-09-27 13:12 UTC|newest]
Thread overview: 88+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-09-16 17:51 [PATCH v3 0/6] iommu: split mapping to page sizes as supported by the hardware Ohad Ben-Cohen
2011-09-16 17:51 ` Ohad Ben-Cohen
2011-09-16 17:51 ` Ohad Ben-Cohen
2011-09-16 17:51 ` [PATCH v3 1/6] iommu/core: " Ohad Ben-Cohen
2011-09-16 17:51 ` Ohad Ben-Cohen
2011-09-16 17:51 ` Ohad Ben-Cohen
2011-09-27 10:05 ` Roedel, Joerg
2011-09-27 10:05 ` Roedel, Joerg
2011-09-27 12:26 ` Ohad Ben-Cohen
2011-09-27 12:26 ` Ohad Ben-Cohen
2011-09-27 13:12 ` Roedel, Joerg [this message]
2011-09-27 13:12 ` Roedel, Joerg
2011-09-27 13:28 ` Ohad Ben-Cohen
2011-09-27 13:28 ` Ohad Ben-Cohen
2011-09-27 18:14 ` Roedel, Joerg
2011-09-27 18:14 ` Roedel, Joerg
2011-10-02 15:58 ` Ohad Ben-Cohen
2011-10-02 15:58 ` Ohad Ben-Cohen
2011-10-02 15:58 ` Ohad Ben-Cohen
2011-10-10 7:40 ` Ohad Ben-Cohen
2011-10-10 7:40 ` Ohad Ben-Cohen
2011-10-10 7:40 ` Ohad Ben-Cohen
2011-10-10 9:47 ` Roedel, Joerg
2011-10-10 9:47 ` Roedel, Joerg
2011-10-10 13:59 ` Ohad Ben-Cohen
2011-10-10 13:59 ` Ohad Ben-Cohen
2011-10-10 15:36 ` Roedel, Joerg
2011-10-10 15:36 ` Roedel, Joerg
2011-10-10 15:36 ` Roedel, Joerg
2011-10-10 17:02 ` Ohad Ben-Cohen
2011-10-10 17:02 ` Ohad Ben-Cohen
2011-10-10 22:01 ` Ohad Ben-Cohen
2011-10-10 22:01 ` Ohad Ben-Cohen
2011-10-11 10:21 ` Roedel, Joerg
2011-10-11 10:21 ` Roedel, Joerg
2011-10-11 10:21 ` Roedel, Joerg
2011-10-11 10:19 ` Roedel, Joerg
2011-10-11 10:19 ` Roedel, Joerg
2011-10-10 22:49 ` Ohad Ben-Cohen
2011-10-10 22:49 ` Ohad Ben-Cohen
2011-10-11 10:38 ` Roedel, Joerg
2011-10-11 10:38 ` Roedel, Joerg
2011-10-11 17:01 ` Ohad Ben-Cohen
2011-10-11 17:01 ` Ohad Ben-Cohen
2011-10-14 13:35 ` Roedel, Joerg
2011-10-14 13:35 ` Roedel, Joerg
2011-10-14 17:03 ` Ohad Ben-Cohen
2011-10-14 17:03 ` Ohad Ben-Cohen
2011-10-14 17:03 ` Ohad Ben-Cohen
2011-10-14 17:05 ` Ohad Ben-Cohen
2011-10-14 17:05 ` Ohad Ben-Cohen
2011-10-14 17:05 ` Ohad Ben-Cohen
2011-10-17 8:05 ` Ohad Ben-Cohen
2011-10-17 8:05 ` Ohad Ben-Cohen
2011-10-17 9:28 ` Roedel, Joerg
2011-10-17 9:28 ` Roedel, Joerg
2011-10-17 9:28 ` Roedel, Joerg
2011-10-17 9:55 ` Ohad Ben-Cohen
2011-10-17 9:55 ` Ohad Ben-Cohen
2011-10-11 14:59 ` KyongHo Cho
2011-10-11 14:59 ` KyongHo Cho
2011-10-11 14:59 ` KyongHo Cho
2011-10-11 17:04 ` Ohad Ben-Cohen
2011-10-11 17:04 ` Ohad Ben-Cohen
2011-10-11 17:04 ` Ohad Ben-Cohen
2011-10-10 12:52 ` KyongHo Cho
2011-10-10 12:52 ` KyongHo Cho
2011-10-10 14:00 ` Ohad Ben-Cohen
2011-10-10 14:00 ` Ohad Ben-Cohen
2011-09-16 17:51 ` [PATCH v3 2/6] iommu/omap: announce supported page sizes Ohad Ben-Cohen
2011-09-16 17:51 ` Ohad Ben-Cohen
2011-09-16 17:51 ` Ohad Ben-Cohen
2011-09-16 17:51 ` [PATCH v3 3/6] iommu/msm: " Ohad Ben-Cohen
2011-09-16 17:51 ` Ohad Ben-Cohen
2011-09-16 17:51 ` Ohad Ben-Cohen
2011-09-25 5:03 ` David Brown
2011-09-25 5:03 ` David Brown
2011-09-16 17:51 ` [PATCH v3 4/6] iommu/amd: " Ohad Ben-Cohen
2011-09-16 17:51 ` Ohad Ben-Cohen
2011-09-16 17:51 ` Ohad Ben-Cohen
2011-09-16 17:51 ` [PATCH v3 5/6] iommu/intel: " Ohad Ben-Cohen
2011-09-16 17:51 ` Ohad Ben-Cohen
2011-09-16 17:51 ` Ohad Ben-Cohen
2011-09-16 17:51 ` [PATCH v3 6/6] iommu/core: remove the temporary register_iommu_pgsize API Ohad Ben-Cohen
2011-09-16 17:51 ` Ohad Ben-Cohen
2011-09-16 17:51 ` Ohad Ben-Cohen
2011-09-27 8:56 ` [PATCH v3 0/6] iommu: split mapping to page sizes as supported by the hardware Ohad Ben-Cohen
2011-09-27 8:56 ` Ohad Ben-Cohen
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