From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from neon.transmeta.com (neon-best.transmeta.com [206.184.214.10]) by kvack.org (8.8.7/8.8.7) with ESMTP id NAA06593 for ; Sun, 30 May 1999 13:47:36 -0400 Date: Sun, 30 May 1999 10:47:06 -0700 (PDT) From: Linus Torvalds Subject: Re: [PATCH] cache large files in the page cache In-Reply-To: Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org To: "Eric W. Biederman" Cc: Jakub Jelinek , linux-kernel@vger.rutgers.edu, linux-mm@kvack.org List-ID: On 30 May 1999, Eric W. Biederman wrote: > > LT> Indeed. An dI would suggest that the shift be limited to at most 9 anyway: > LT> right now I applied the part that disallows non-page-aligned offsets, but > LT> I think that we may in the future allow anonymous mappings again at finer > LT> granularity (somebody made a really good argument about wine for this). > > I'd love to hear the argument. Something that would negate the disadvantage > of ntuple buffering, and the need for reverse page maps, and isn't portable. Wine. Mapping windows binaries in a Linux address space. Portability is a non-issue: this would only work on a 386, and only on Linux anyway (MAYBE on other architectures Wine supports, but that's their problem). Windows binaries are _not_ nicely aligned like the Linux ones. They are often 512-byte aligned. Yes, we can read them in. That is slow as hell, and doesn't allow sharing. Bad. > Well, currectly supporting non-aligned mappings needs more than just a > few extra bits. The code to update all mappings on write, and the > ability to ensure that a given byte is only faulted in for a single > offset at a time. (Admittedly if everything is a read mapping you > can be a smidge more lax). We would not guarantee write coherency for anything but the page-aligned case. Linus -- To unsubscribe, send a message with 'unsubscribe linux-mm my@address' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://humbolt.geo.uu.nl/Linux-MM/