From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id E0AADC433F5 for ; Mon, 22 Nov 2021 09:22:56 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 70ADC6B0071; Mon, 22 Nov 2021 04:22:41 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 6BAAF6B0072; Mon, 22 Nov 2021 04:22:41 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 5A9886B0073; Mon, 22 Nov 2021 04:22:41 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0007.hostedemail.com [216.40.44.7]) by kanga.kvack.org (Postfix) with ESMTP id 4C6A96B0071 for ; Mon, 22 Nov 2021 04:22:41 -0500 (EST) Received: from smtpin12.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id 147448248D52 for ; Mon, 22 Nov 2021 09:22:31 +0000 (UTC) X-FDA: 78836025660.12.4DCFEA2 Received: from gentwo.de (gentwo.de [161.97.139.209]) by imf18.hostedemail.com (Postfix) with ESMTP id A583D400209D for ; Mon, 22 Nov 2021 09:22:28 +0000 (UTC) Received: by gentwo.de (Postfix, from userid 1001) id 646C5B003B1; Mon, 22 Nov 2021 10:22:28 +0100 (CET) Received: from localhost (localhost [127.0.0.1]) by gentwo.de (Postfix) with ESMTP id 62F82B002E6; Mon, 22 Nov 2021 10:22:28 +0100 (CET) Date: Mon, 22 Nov 2021 10:22:28 +0100 (CET) From: Christoph Lameter X-X-Sender: cl@gentwo.de To: Rustam Kovhaev cc: vbabka@suse.cz, penberg@kernel.org, rientjes@google.com, iamjoonsoo.kim@lge.com, akpm@linux-foundation.org, corbet@lwn.net, djwong@kernel.org, david@fromorbit.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-doc@vger.kernel.org, gregkh@linuxfoundation.org, viro@zeniv.linux.org.uk, dvyukov@google.com Subject: Re: [PATCH v4] slob: add size header to all allocations In-Reply-To: <20211122013026.909933-1-rkovhaev@gmail.com> Message-ID: References: <037227db-c869-7d9c-65e8-8f5f8682171d@suse.cz> <20211122013026.909933-1-rkovhaev@gmail.com> User-Agent: Alpine 2.22 (DEB 394 2020-01-19) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: A583D400209D X-Stat-Signature: gei4ibjk11aqa84hquyqjnimc4jg35so Authentication-Results: imf18.hostedemail.com; dkim=none; spf=none (imf18.hostedemail.com: domain of cl@gentwo.org has no SPF policy when checking 161.97.139.209) smtp.mailfrom=cl@gentwo.org; dmarc=none X-HE-Tag: 1637572948-369001 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Sun, 21 Nov 2021, Rustam Kovhaev wrote: > Let's prepend both kmalloc() and kmem_cache_alloc() allocations with the > size header. > It simplifies the slab API and guarantees that both kmem_cache_alloc() > and kmalloc() memory could be freed by kfree(). > > meminfo right after the system boot, x86-64 on xfs, without the patch: > Slab: 34700 kB > > the same, with the patch: > Slab: 35752 kB > +#define SLOB_HDR_SIZE max(ARCH_KMALLOC_MINALIGN, ARCH_SLAB_MINALIGN) Ok that is up to 128 bytes on some architectues. Mostly 32 or 64 bytes. > @@ -307,6 +303,7 @@ static void *slob_alloc(size_t size, gfp_t gfp, int align, int node, > unsigned long flags; > bool _unused; > > + size += SLOB_HDR_SIZE; And every object now has this overhead? 128 bytes extra in extreme cases per object? > - if (size < PAGE_SIZE - minalign) { > - int align = minalign; > + if (size < PAGE_SIZE - SLOB_HDR_SIZE) { > + int align = SLOB_HDR_SIZE; And the object is also aligned to 128 bytes boundaries on some architectures. So a 4 byte object occupies 256 bytes in SLOB? SLOB will no longer be a low memory overhead allocator then.