From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pa0-f54.google.com (mail-pa0-f54.google.com [209.85.220.54]) by kanga.kvack.org (Postfix) with ESMTP id 61FFA6B00AE for ; Thu, 17 Oct 2013 15:01:41 -0400 (EDT) Received: by mail-pa0-f54.google.com with SMTP id kx10so3244360pab.27 for ; Thu, 17 Oct 2013 12:01:41 -0700 (PDT) Date: Thu, 17 Oct 2013 19:01:38 +0000 From: Christoph Lameter Subject: Re: [PATCH v2 3/5] slab: restrict the number of objects in a slab In-Reply-To: <1381989797-29269-4-git-send-email-iamjoonsoo.kim@lge.com> Message-ID: <00000141c7cb668b-1e2528ea-ce87-4380-a0dd-e5be9384cd84-000000@email.amazonses.com> References: <1381989797-29269-1-git-send-email-iamjoonsoo.kim@lge.com> <1381989797-29269-4-git-send-email-iamjoonsoo.kim@lge.com> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org List-ID: To: Joonsoo Kim Cc: Pekka Enberg , Andrew Morton , Joonsoo Kim , David Rientjes , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Wanpeng Li n Thu, 17 Oct 2013, Joonsoo Kim wrote: > To prepare to implement byte sized index for managing the freelist > of a slab, we should restrict the number of objects in a slab to be less > or equal to 256, since byte only represent 256 different values. > Setting the size of object to value equal or more than newly introduced > SLAB_MIN_SIZE ensures that the number of objects in a slab is less or > equal to 256 for a slab with 1 page. Ok so that results in a mininum size object size of 2^(12 - 8) = 2^4 == 16 bytes on x86. This is not true for order 1 pages (which SLAB also supports) where we need 32 bytes. Problems may arise on PPC or IA64 where the page size may be larger than 64K. With 64K we have a mininum size of 2^(16 - 8) = 256 bytes. For those arches we may need 16 bit sized indexes. Maybe make that compile time determined base on page size? > 64KByte results in 16 bit sized indexes? Otherwise I like this approach. Simplifies a lot and its very cache friendly. -- 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/ . Don't email: email@kvack.org