From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Fri, 02 Aug 2002 16:54:53 -0700 From: "Martin J. Bligh" Subject: Re: large page patch (fwd) (fwd) Message-ID: <92200000.1028332493@flay> In-Reply-To: References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline Sender: owner-linux-mm@kvack.org Return-Path: To: Linus Torvalds Cc: Hubertus Franke , wli@holomorpy.com, gh@us.ibm.com, akpm@zip.com.au, swj@cse.unsw.edu.au, linux-mm mailing list List-ID: >> Let me than turn around the table. Have you looked at our patch for 2.4.18. >> It doesn't add anything to the hot path either, if the (vma->pg_order == 0). >> Period. > > Nobody has forwarded the patch, and I've seen no discussion of it on the > kernel mailing lists. > > Guess what the answer is? > > Is it 10 lines of code in the VM subsystem? No, and you're not going to like the patch in it's current incarnation by the sound of it. So, having listened to your objections, we're going to take a slightly different course - we will prepare a minimal version of the patch with very low impact on the core VM code, but using more standard interfaces to access it (eg the shmem method you outlined earlier). It'll have a little less functionality, but so be it. There are other apps apart from Oracle that want the ability to use large pages (eg DB2 and Java), and it seems that most of those want them for anonymous mmap or shmem. If we can provide an interface that's more standard, it'll make people's porting much easier. IBM Research has done some significant benchmarking of large page support in a variety of applications, and has seen 20-40% performance boost for Java, and 6-22% improvment for the SPEC CPU2000 set of tests. For the full details, see the OLS paper at: http://www.linux.org.uk/~ajh/ols2002_proceedings.pdf.gz Moreover, we need large pages to reduce PTE consumption in a variety of applications using shared memory, especially given the additional overhead of rmap. We should have this available in a few days - if you could hold off until then, we should be able to do an objective comparison? I believe we can make something that's acceptable to you. Thanks, Martin. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/