From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-f199.google.com (mail-pf0-f199.google.com [209.85.192.199]) by kanga.kvack.org (Postfix) with ESMTP id E20726B0008 for ; Mon, 28 May 2018 12:03:50 -0400 (EDT) Received: by mail-pf0-f199.google.com with SMTP id e20-v6so7606306pff.14 for ; Mon, 28 May 2018 09:03:50 -0700 (PDT) Received: from mx2.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id h9-v6si8037304pgc.597.2018.05.28.09.03.49 for (version=TLS1 cipher=AES128-SHA bits=128/128); Mon, 28 May 2018 09:03:49 -0700 (PDT) Subject: Re: [RFC PATCH 1/5] mm, slab/slub: introduce kmalloc-reclaimable caches References: <20180524110011.1940-1-vbabka@suse.cz> <20180524110011.1940-2-vbabka@suse.cz> <0100016397ffdbf2-dc8a305f-efa8-4771-9f2a-3a7568693db4-000000@email.amazonses.com> From: Vlastimil Babka Message-ID: <99bb1e0c-15e2-7f8a-19ea-7cf9f49551b1@suse.cz> Date: Mon, 28 May 2018 10:03:48 +0200 MIME-Version: 1.0 In-Reply-To: <0100016397ffdbf2-dc8a305f-efa8-4771-9f2a-3a7568693db4-000000@email.amazonses.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Christopher Lameter Cc: linux-mm@kvack.org, Roman Gushchin , Michal Hocko , Johannes Weiner , linux-kernel@vger.kernel.org, linux-api@vger.kernel.org, Pekka Enberg , David Rientjes , Joonsoo Kim , Mel Gorman , Vijayanand Jitta On 05/25/2018 05:51 PM, Christopher Lameter wrote: > On Thu, 24 May 2018, Vlastimil Babka wrote: > >> diff --git a/include/linux/slab.h b/include/linux/slab.h >> index 9ebe659bd4a5..5bff0571b360 100644 >> --- a/include/linux/slab.h >> +++ b/include/linux/slab.h >> @@ -296,11 +296,16 @@ static inline void __check_heap_object(const void *ptr, unsigned long n, >> (KMALLOC_MIN_SIZE) : 16) >> >> #ifndef CONFIG_SLOB >> -extern struct kmem_cache *kmalloc_caches[KMALLOC_SHIFT_HIGH + 1]; >> +extern struct kmem_cache *kmalloc_caches[2][KMALLOC_SHIFT_HIGH + 1]; >> #ifdef CONFIG_ZONE_DMA >> extern struct kmem_cache *kmalloc_dma_caches[KMALLOC_SHIFT_HIGH + 1]; >> #endif > > In the existing code we used a different array name for the DMA caches. > This is a similar situation. > > I would suggest to use > > kmalloc_reclaimable_caches[] > > or make it consistent by folding the DMA caches into the array too (but > then note the issues below). > >> @@ -536,12 +541,13 @@ static __always_inline void *kmalloc(size_t size, gfp_t flags) >> #ifndef CONFIG_SLOB >> if (!(flags & GFP_DMA)) { >> unsigned int index = kmalloc_index(size); >> + unsigned int recl = kmalloc_reclaimable(flags); > > This is a hotpath reserved for regular allocations. The reclaimable slabs > need to be handled like the DMA slabs. So check for GFP_DMA plus the > reclaimable flags. Yeah I thought that by doing reclaimable via array index manipulation and not a branch, there would be no noticeable overhead. And GFP_DMA should go away eventually. I will see if I can convert GFP_DMA to another index, and completely remove the branch quoted above. >> @@ -588,12 +594,13 @@ static __always_inline void *kmalloc_node(size_t size, gfp_t flags, int node) >> if (__builtin_constant_p(size) && >> size <= KMALLOC_MAX_CACHE_SIZE && !(flags & GFP_DMA)) { >> unsigned int i = kmalloc_index(size); >> + unsigned int recl = kmalloc_reclaimable(flags); >> > > > Same situation here and additional times below. >