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Thu, 01 Sep 2022 04:14:46 -0700 (PDT) Date: Thu, 1 Sep 2022 20:14:40 +0900 From: Hyeonggon Yoo <42.hyeyoo@gmail.com> To: Feng Tang Cc: Andrew Morton , Vlastimil Babka , Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim , Roman Gushchin , Dmitry Vyukov , "Hansen, Dave" , "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" , Robin Murphy , John Garry , Kefeng Wang Subject: Re: [PATCH v4 1/4] mm/slub: enable debugging memory wasting of kmalloc Message-ID: References: <20220829075618.69069-1-feng.tang@intel.com> <20220829075618.69069-2-feng.tang@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1662030889; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; 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dmarc=pass (policy=none) header.from=gmail.com X-Rspamd-Server: rspam11 X-Stat-Signature: ntmk9x5ooqau9i6edz38kmkwsd89nu33 X-Rspamd-Queue-Id: 5AACF20032 X-Rspam-User: X-HE-Tag: 1662030889-866409 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 Thu, Sep 01, 2022 at 01:04:58PM +0800, Feng Tang wrote: > On Wed, Aug 31, 2022 at 10:52:15PM +0800, Hyeonggon Yoo wrote: > > On Mon, Aug 29, 2022 at 03:56:15PM +0800, Feng Tang wrote: > > > kmalloc's API family is critical for mm, with one nature that it will > > > round up the request size to a fixed one (mostly power of 2). Say > > > when user requests memory for '2^n + 1' bytes, actually 2^(n+1) bytes > > > could be allocated, so in worst case, there is around 50% memory > > > space waste. > > > > > > > [...] > > > > > static void *___slab_alloc(struct kmem_cache *s, gfp_t gfpflags, int node, > > > - unsigned long addr, struct kmem_cache_cpu *c) > > > + unsigned long addr, struct kmem_cache_cpu *c, unsigned int orig_size) > > > { > > > void *freelist; > > > struct slab *slab; > > > @@ -3115,6 +3158,7 @@ static void *___slab_alloc(struct kmem_cache *s, gfp_t gfpflags, int node, > > > > > > if (s->flags & SLAB_STORE_USER) > > > set_track(s, freelist, TRACK_ALLOC, addr); > > > + set_orig_size(s, freelist, orig_size); > > > > > > return freelist; > > > } > > > @@ -3140,6 +3184,8 @@ static void *___slab_alloc(struct kmem_cache *s, gfp_t gfpflags, int node, > > > */ > > > if (s->flags & SLAB_STORE_USER) > > > set_track(s, freelist, TRACK_ALLOC, addr); > > > + set_orig_size(s, freelist, orig_size); > > > + > > > return freelist; > > > } > > > > Maybe we can move set_track() and set_orig_size() to after slab_post_alloc_hook(). > > something like alloc/free hooks for debugging caches? (and drop orig_size parameter.) > > Yep, we discussed this during v3 review > https://lore.kernel.org/lkml/442d2b9c-9f07-8954-b90e-b4a9f8b64303@intel.com/ Ah, I missed that :) Thanks! Considering the added cost (should be low) and races with validation, I think this approach will cost more than it get. Sorry for the noise. p.s. I think I can review this series in few days. Thanks for your efforts! > Will revisit this considering recent refactoring and the following > kmalloc data redzone patches. > Thanks, > Feng > > > Thanks! -- Thanks, Hyeonggon