From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from ozlabs.org (ozlabs.org [IPv6:2401:3900:2:1::2]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 4E9A31A0061 for ; Tue, 2 Feb 2016 12:08:31 +1100 (AEDT) Date: Tue, 2 Feb 2016 12:04:47 +1100 From: David Gibson To: Anshuman Khandual Cc: paulus@samba.org, mpe@ellerman.id.au, benh@kernel.crashing.org, aik@ozlabs.ru, lvivier@redhat.com, thuth@redhat.com, linuxppc-dev@lists.ozlabs.org Subject: Re: [RFCv2 5/9] arch/powerpc: Split hash page table sizing heuristic into a helper Message-ID: <20160202010447.GC15080@voom.fritz.box> References: <1454045043-25545-1-git-send-email-david@gibson.dropbear.id.au> <1454045043-25545-6-git-send-email-david@gibson.dropbear.id.au> <56AF0380.3020500@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="mvpLiMfbWzRoNl4x" In-Reply-To: <56AF0380.3020500@linux.vnet.ibm.com> List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , --mvpLiMfbWzRoNl4x Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Mon, Feb 01, 2016 at 12:34:32PM +0530, Anshuman Khandual wrote: > On 01/29/2016 10:53 AM, David Gibson wrote: > > htab_get_table_size() either retrieve the size of the hash page table (= HPT) > > from the device tree - if the HPT size is determined by firmware - or > > uses a heuristic to determine a good size based on RAM size if the kern= el > > is responsible for allocating the HPT. > >=20 > > To support a PAPR extension allowing resizing of the HPT, we're going to > > want the memory size -> HPT size logic elsewhere, so split it out into a > > helper function. > >=20 > > Signed-off-by: David Gibson > > --- > > arch/powerpc/include/asm/mmu-hash64.h | 3 +++ > > arch/powerpc/mm/hash_utils_64.c | 30 +++++++++++++++++----------= --- > > 2 files changed, 20 insertions(+), 13 deletions(-) > >=20 > > diff --git a/arch/powerpc/include/asm/mmu-hash64.h b/arch/powerpc/inclu= de/asm/mmu-hash64.h > > index 7352d3f..cf070fd 100644 > > --- a/arch/powerpc/include/asm/mmu-hash64.h > > +++ b/arch/powerpc/include/asm/mmu-hash64.h > > @@ -607,6 +607,9 @@ static inline unsigned long get_kernel_vsid(unsigne= d long ea, int ssize) > > context =3D (MAX_USER_CONTEXT) + ((ea >> 60) - 0xc) + 1; > > return get_vsid(context, ea, ssize); > > } > > + > > +unsigned htab_shift_for_mem_size(unsigned long mem_size); > > + > > #endif /* __ASSEMBLY__ */ > > =20 > > #endif /* _ASM_POWERPC_MMU_HASH64_H_ */ > > diff --git a/arch/powerpc/mm/hash_utils_64.c b/arch/powerpc/mm/hash_uti= ls_64.c > > index e88a86e..d63f7dc 100644 > > --- a/arch/powerpc/mm/hash_utils_64.c > > +++ b/arch/powerpc/mm/hash_utils_64.c > > @@ -606,10 +606,24 @@ static int __init htab_dt_scan_pftsize(unsigned l= ong node, > > return 0; > > } > > =20 > > -static unsigned long __init htab_get_table_size(void) > > +unsigned htab_shift_for_mem_size(unsigned long mem_size) > > { > > - unsigned long mem_size, rnd_mem_size, pteg_count, psize; > > + unsigned memshift =3D __ilog2(mem_size); > > + unsigned pshift =3D mmu_psize_defs[mmu_virtual_psize].shift; > > + unsigned pteg_shift; > > + > > + /* round mem_size up to next power of 2 */ > > + if ((1UL << memshift) < mem_size) > > + memshift +=3D 1; > > + > > + /* aim for 2 pages / pteg */ >=20 > While here I guess its a good opportunity to write couple of lines > about why one PTE group for every two physical pages on the system, Well, that don't really know, it's just copied from the existing code. > why minimum (1UL << 11 =3D 2048) number of PTE groups required, Ok. > why > (1U << 7 =3D 128) entries per PTE group Um.. what? Because that's how big a PTEG is, I don't think re-explaining the HPT structure here is useful. > and also remove the existing > confusing comments above ? Just a suggestion. Not sure which comment you mean. >=20 > > + pteg_shift =3D memshift - (pshift + 1); > > + > > + return max(pteg_shift + 7, 18U); > > +} > > =20 > > +static unsigned long __init htab_get_table_size(void) > > +{ > > /* If hash size isn't already provided by the platform, we try to > > * retrieve it from the device-tree. If it's not there neither, we > > * calculate it now based on the total RAM size > > @@ -619,17 +633,7 @@ static unsigned long __init htab_get_table_size(vo= id) > > if (ppc64_pft_size) > > return 1UL << ppc64_pft_size; > > =20 > > - /* round mem_size up to next power of 2 */ > > - mem_size =3D memblock_phys_mem_size(); > > - rnd_mem_size =3D 1UL << __ilog2(mem_size); > > - if (rnd_mem_size < mem_size) > > - rnd_mem_size <<=3D 1; > > - > > - /* # pages / 2 */ > > - psize =3D mmu_psize_defs[mmu_virtual_psize].shift; > > - pteg_count =3D max(rnd_mem_size >> (psize + 1), 1UL << 11); > > - > > - return pteg_count << 7; > > + return htab_shift_for_mem_size(memblock_phys_mem_size()); >=20 > Would it be 1UL << htab_shift_for_mem_size(memblock_phys_mem_size()) > instead ? It was returning the size of the HPT not the shift of HPT > originally or I am missing something here. Oops, yes. That would have broken all non-LPAR platforms. --=20 David Gibson | I'll have my music baroque, and my code david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_ | _way_ _around_! http://www.ozlabs.org/~dgibson --mvpLiMfbWzRoNl4x Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v1 iQIcBAEBAgAGBQJWsACvAAoJEGw4ysog2bOSU2UQALHKvuDWfoBhdWJ79NLGVQK2 j7+V8PYa6TTjKl5hsBFtcAQuXjVC9grwwVdOOuJxvlpuatdmYIY8U8P0yB99VcQ2 qdDjdggU/SsUj/JdrOx55fRnzR4DoFcCZQtgiBSErT17576N51XYN1XsQU3afdBO jYnwLqJZ2K6bjqd7jfodifLJTUEeM3ayv03I/x1wn1fJnF1gevLmgDmHQSjgej2w 7SPZn27mKO/J3TUu4xTVhhSSn/mlNLuhBuvQlLAWAcBj/xFIRXt0LAPHeQtfH2Kg 0qT9fAvLUaiAULY3cM5+rqOv/eeeQ6O/GIqM1trnDtpxzip2jfu+OFzQdUWpWgXG BiPKlyDB0dgwC5ZM0zpSNNqMapyIgsfzP23OndbbMJpUbMtj2AaEW9pzk84iirQB Fmyqe3lCYetn10uKbrULcqLjDPklwFzOXa5IktpkuLuZn94u0mi3S0L8R9qEJcMk ZDsDCOZ9DlGXn5EjrCujWFVz3hGAIk7393ksFp2VRew0Fl0opnZpFhHeZ+hDfTdy Ap8yWf5T6it4bQcE9RcApnxXn/5CX9Cce1NIZUYU7oA8qwydFfLm3iZ2x5K3Ye40 rFVcCaBKPP+yl3SK+kfZbCeJSgSQCpKJga3nhcXLTAhhh4YW+ZZ3gCLwOpLsgg8i cyL4dDNWrcyfBqsY04Lz =FMYh -----END PGP SIGNATURE----- --mvpLiMfbWzRoNl4x--