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 983446B0166 for ; Fri, 18 Oct 2013 11:12:58 -0400 (EDT) Received: by mail-pa0-f54.google.com with SMTP id kx10so4690097pab.13 for ; Fri, 18 Oct 2013 08:12:58 -0700 (PDT) Received: from psmtp.com ([74.125.245.204]) by mx.google.com with SMTP id z1si1155655pbw.99.2013.10.18.08.12.56 for ; Fri, 18 Oct 2013 08:12:57 -0700 (PDT) Received: by mail-we0-f170.google.com with SMTP id u57so3964111wes.1 for ; Fri, 18 Oct 2013 08:12:55 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: <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> <00000141c7cb668b-1e2528ea-ce87-4380-a0dd-e5be9384cd84-000000@email.amazonses.com> Date: Sat, 19 Oct 2013 00:12:54 +0900 Message-ID: Subject: Re: [PATCH v2 3/5] slab: restrict the number of objects in a slab From: JoonSoo Kim Content-Type: text/plain; charset=ISO-8859-1 Sender: owner-linux-mm@kvack.org List-ID: To: Christoph Lameter Cc: Joonsoo Kim , Pekka Enberg , Andrew Morton , David Rientjes , Linux Memory Management List , LKML , Wanpeng Li 2013/10/18 Christoph Lameter : > 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. According to current slab size calculating logic, slab whose object size is less or equal to 16 bytes use only order 0 page. So there is no problem. > 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? Okay. I will try it. > Otherwise I like this approach. Simplifies a lot and its very cache > friendly. Thanks. -- 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