From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dave Hansen Date: Thu, 31 Aug 2006 17:57:38 +0000 Subject: Re: [RFC][PATCH 3/9] actual generic PAGE_SIZE infrastructure Message-Id: <1157047058.31295.28.camel@localhost.localdomain> List-Id: References: <20060830221604.E7320C0F@localhost.localdomain> <20060830221606.40937644@localhost.localdomain> In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Christoph Lameter Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-ia64@vger.kernel.org On Wed, 2006-08-30 at 17:08 -0700, Christoph Lameter wrote: > On Wed, 30 Aug 2006, Dave Hansen wrote: > > > #endif /* CONFIG_ARCH_HAVE_GET_ORDER */ > > -#endif /* __ASSEMBLY__ */ > > +#endif /* __ASSEMBLY__ */ > ^^^ Extra blank. OK. I'll fix that. > > + prompt "Kernel Page Size" > page size? Sure. > > + This lets you select the page size of the kernel. For best > > + 32-bit compatibility on 64-bit architectures, a page size of 4KB > > + should be selected (although most binaries work perfectly fine with > > + a larger page size). For best performance, a page size of larger > > + than 4KB is recommended. However, there are a number of > > + side-effects of larger page sizes, like small files fitting poorly > > + into the page cache. > > Could we change this somewhat? Avoid the direct address and maybe say: > > The kernel page size determines the basic chunk of memory handled > by the Linux VM. The bigger the page size the less page objects > have to be managed by the kernel which reduces the VM overhead in > handling large amounts of data. However, larger pages also lead > to memory being wasted by the kernel since small files will > at mininum require one page of memory. A 4K pagesize is fairly standard > and may be required for 32 bit compatibility on many platforms. > > It is usually not wise to select another page size than the default > unless one knows what one is doing or has some time to spend on > getting to know the kernel. This is very nice. I'll incorporate it. > Note that the default pagesize on IA64 is 16K and some important things > would change if a lesser size is selected. I have never run a 4K kernel. > I do not think we can just say that 4KB is okay. There may be other > platforms that have other default page sizes. If we can't just say that it is OK, then we should probably disable it in Kconfig. Should we do that? -- Dave