From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Subject: Re: [PATCH 1/6] powerpc: Make NR_IRQS a CONFIG option From: Michael Ellerman To: Grant Likely In-Reply-To: References: Content-Type: multipart/signed; micalg="pgp-sha1"; protocol="application/pgp-signature"; boundary="=-62l9smU8SMSnAB72veqT" Date: Thu, 15 Oct 2009 10:47:52 +1100 Message-Id: <1255564072.9651.10.camel@concordia> Mime-Version: 1.0 Cc: linuxppc-dev@ozlabs.org Reply-To: michael@ellerman.id.au List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , --=-62l9smU8SMSnAB72veqT Content-Type: text/plain Content-Transfer-Encoding: quoted-printable On Wed, 2009-10-14 at 12:59 -0600, Grant Likely wrote: > On Tue, Oct 13, 2009 at 11:44 PM, Michael Ellerman > wrote: > > The irq_desc array consumes quite a lot of space, and for systems > > that don't need or can't have 512 irqs it's just wasted space. > > > > The first 16 are reserved for ISA, so the minimum of 32 is really > > 16 - and no one has asked for more than 512 so leave that as the > > maximum. >=20 > Does it really make sense to have this as a user twiddlable value? > Especially when many users just don't have the background to know what > an appropriate value is here and will get it wrong? I believe your > sparse IRQ patch has a bigger impact anyway on systems where memory is > tight. We have users? But yes I think it's reasonable, there's a million other options people can fiddle with and break their kernel, I don't see that this is much different. The sparse IRQ patch has a bigger difference on the size of the irq_desc array, but there are still other things that are statically sized based on NR_IRQs. So if you're building an machine-specific kernel and you know you're only going to have N interrupts, then this will give you a bigger saving. But I'm not super fussed, if other people think it's too dangerous we can drop it. cheers --=-62l9smU8SMSnAB72veqT Content-Type: application/pgp-signature; name="signature.asc" Content-Description: This is a digitally signed message part -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.9 (GNU/Linux) iEYEABECAAYFAkrWYyUACgkQdSjSd0sB4dIiEACfevng5ge/kWXo6vRaGEhuecgV w4IAn1Jy0ZP2+afXb2aCY/gsypt5LcHu =o/3T -----END PGP SIGNATURE----- --=-62l9smU8SMSnAB72veqT--