| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Date: 21 Mar 2008 22:25:47 +0100 From: Andi Kleen <andi@...stfloor.org> To: Christoph Lameter <clameter@....com> Cc: linux-mm@...ck.org, linux-kernel@...r.kernel.org Subject: Re: [13/14] vcompound: Use vcompound for swap_map Christoph Lameter <clameter@....com> writes: > Use virtual compound pages for the large swap maps. This only works for > swap maps that are smaller than a MAX_ORDER block though. If the swap map > is larger then there is no way around the use of vmalloc. Have you considered the potential memory wastage from rounding up to the next page order now? (similar in all the other patches to change vmalloc). e.g. if the old size was 64k + 1 byte it will suddenly get 128k now. That is actually not a uncommon situation in my experience; there are often power of two buffers with some small headers. A long time ago (in 2.4-aa) I did something similar for module loading as an experiment to avoid too many TLB misses. The module loader would first try to get a continuous range in the direct mapping and only then fall back to vmalloc. But I used a simple trick to avoid the waste problem: it allocated a continuous range rounded up to the next page-size order and then freed the excess pages back into the page allocator. That was called alloc_exact(). If you replace vmalloc with alloc_pages you should use something like that too I think. -Andi -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Powered by blists - more mailing lists