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Sun, 28 Aug 2022 20:19:02 -0700 (PDT) Date: Mon, 29 Aug 2022 12:18:57 +0900 From: Hyeonggon Yoo <42.hyeyoo@gmail.com> To: Dawei Li Cc: cl@linux.com, penberg@kernel.org, rientjes@google.com, iamjoonsoo.kim@lge.com, akpm@linux-foundation.org, vbabka@suse.cz, roman.gushchin@linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm: simplify size2index conversion of __kmalloc_index Message-ID: References: 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=1661743144; 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; bh=r0M9FUvZOZnp7Vmf7xtDgyqRqSJWKApPfYbePi7+It4=; b=exADepBmatPdDoku0/hHWzFYXfZSkvmFRycuBy0mqtj4TkL9Oi3xcc1lTONgIkOdswDfM2 sy+Sg7X6ezE99KWguTEzHrnW1F+guZam3eUbsS4x8a1Wi4qGz/sFmTluIawU6gwhPIb4X4 Lgx9pb1+GPJojWgTC6SlUHCfbesF2pw= ARC-Authentication-Results: i=1; imf15.hostedemail.com; dkim=pass header.d=gmail.com header.s=20210112 header.b=kj4Df5cr; dmarc=pass (policy=none) header.from=gmail.com; spf=pass (imf15.hostedemail.com: domain of 42.hyeyoo@gmail.com designates 209.85.216.50 as permitted sender) smtp.mailfrom=42.hyeyoo@gmail.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1661743144; a=rsa-sha256; cv=none; b=3H5Y5I8utCqDSC+4LWCnEapDF9bkKMsLmKUG1/e+ejmWmPsvQF8bIpUzZRk8j84qzndHvT g2g2zyLFkHUhGvpRMOk5lcTGFJWmYhkPqK5Wrp7rfbQxd9RKLSyqSSi66pBA2vErZDC2tx Tc1nZWpOkdbOft27i2ElpBozEUBWAmE= X-Stat-Signature: w39cax9jrn4iq7t5mo794u1yseim9h6a X-Rspamd-Queue-Id: 98AC6A0030 Authentication-Results: imf15.hostedemail.com; dkim=pass header.d=gmail.com header.s=20210112 header.b=kj4Df5cr; dmarc=pass (policy=none) header.from=gmail.com; spf=pass (imf15.hostedemail.com: domain of 42.hyeyoo@gmail.com designates 209.85.216.50 as permitted sender) smtp.mailfrom=42.hyeyoo@gmail.com X-Rspamd-Server: rspam03 X-Rspam-User: X-HE-Tag: 1661743144-455703 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, Aug 28, 2022 at 11:14:48PM +0800, Dawei Li wrote: > Current size2index is implemented by one to one hardcode mapping, > which can be improved by order_base_2(). > Must be careful to not violate compile-time optimization rule. > Generated code for caller of kmalloc: > 48 8b 3d 9f 0b 6b 01 mov 0x16b0b9f(%rip),%rdi > # ffffffff826d1568 > ba 08 01 00 00 mov $0x108,%edx > be c0 0d 00 00 mov $0xdc0,%esi > e8 98 d7 2e 00 callq ffffffff8130e170 > > Signed-off-by: Dawei Li > --- > include/linux/slab.h | 34 +++++++++------------------------- > 1 file changed, 9 insertions(+), 25 deletions(-) > > diff --git a/include/linux/slab.h b/include/linux/slab.h > index 0fefdf528e0d..66452a4357c6 100644 > --- a/include/linux/slab.h > +++ b/include/linux/slab.h > @@ -17,7 +17,7 @@ > #include > #include > #include > - > +#include > > /* > * Flags to pass to kmem_cache_create(). > @@ -394,31 +394,16 @@ static __always_inline unsigned int __kmalloc_index(size_t size, > > if (KMALLOC_MIN_SIZE <= 32 && size > 64 && size <= 96) > return 1; > + > if (KMALLOC_MIN_SIZE <= 64 && size > 128 && size <= 192) > return 2; > - if (size <= 8) return 3; > - if (size <= 16) return 4; > - if (size <= 32) return 5; > - if (size <= 64) return 6; > - if (size <= 128) return 7; > - if (size <= 256) return 8; > - if (size <= 512) return 9; > - if (size <= 1024) return 10; > - if (size <= 2 * 1024) return 11; > - if (size <= 4 * 1024) return 12; > - if (size <= 8 * 1024) return 13; > - if (size <= 16 * 1024) return 14; > - if (size <= 32 * 1024) return 15; > - if (size <= 64 * 1024) return 16; > - if (size <= 128 * 1024) return 17; > - if (size <= 256 * 1024) return 18; > - if (size <= 512 * 1024) return 19; > - if (size <= 1024 * 1024) return 20; > - if (size <= 2 * 1024 * 1024) return 21; > - if (size <= 4 * 1024 * 1024) return 22; > - if (size <= 8 * 1024 * 1024) return 23; > - if (size <= 16 * 1024 * 1024) return 24; > - if (size <= 32 * 1024 * 1024) return 25; It does not apply. better rebase it on Vlastimil's slab tree (for-next branch) https://git.kernel.org/pub/scm/linux/kernel/git/vbabka/slab.git/ > + > + if (size <= 8) > + return 3; > + > + /* Following compile-time optimization rule is mandatory. */ > + if (size <= 32 * 1024 * 1024) > + return order_base_2(size); Oh, it seems order_base_2() does compile-time opitmization as well. With order_base_2(), what about using KMALLOC_MAX_CACHE_SIZE instead of 32 * 1024 * 1024? I think that would be more robust. Hmm also better check if it works okay with kfence tests (it passes non-constant value) let't check if it breaks after rebase. Thanks! > > if (!IS_ENABLED(CONFIG_PROFILE_ALL_BRANCHES) && size_is_constant) > BUILD_BUG_ON_MSG(1, "unexpected size in kmalloc_index()"); > @@ -700,7 +685,6 @@ static inline __alloc_size(1, 2) void *kcalloc_node(size_t n, size_t size, gfp_t > return kmalloc_array_node(n, size, flags | __GFP_ZERO, node); > } > > - > #ifdef CONFIG_NUMA > extern void *__kmalloc_node_track_caller(size_t size, gfp_t flags, int node, > unsigned long caller) __alloc_size(1); > -- > 2.25.1 > -- Thanks, Hyeonggon