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[209.85.167.43]) by smtp.gmail.com with ESMTPSA id bi32-20020a05651c232000b0024dba831e9bsm1073183ljb.135.2022.04.20.12.33.55 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 20 Apr 2022 12:33:57 -0700 (PDT) Received: by mail-lf1-f43.google.com with SMTP id x33so4821992lfu.1 for ; Wed, 20 Apr 2022 12:33:55 -0700 (PDT) X-Received: by 2002:a05:6512:108b:b0:470:90b9:fb51 with SMTP id j11-20020a056512108b00b0047090b9fb51mr14612420lfg.52.1650483235692; Wed, 20 Apr 2022 12:33:55 -0700 (PDT) MIME-Version: 1.0 References: In-Reply-To: From: Linus Torvalds Date: Wed, 20 Apr 2022 12:33:39 -0700 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH 07/10] crypto: Use ARCH_DMA_MINALIGN instead of ARCH_KMALLOC_MINALIGN To: Catalin Marinas Cc: Ard Biesheuvel , Herbert Xu , Will Deacon , Marc Zyngier , Arnd Bergmann , Greg Kroah-Hartman , Andrew Morton , Linux Memory Management List , Linux ARM , Linux Kernel Mailing List , "David S. Miller" Content-Type: text/plain; charset="UTF-8" X-Rspam-User: X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 5AA5110001F X-Stat-Signature: oqhrr4iem9gifcn1ds73y4dhk1eijiqt Authentication-Results: imf14.hostedemail.com; dkim=pass header.d=linux-foundation.org header.s=google header.b=Nkom6JPj; dmarc=none; spf=pass (imf14.hostedemail.com: domain of torvalds@linuxfoundation.org designates 209.85.208.180 as permitted sender) smtp.mailfrom=torvalds@linuxfoundation.org X-HE-Tag: 1650483240-399091 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 Wed, Apr 20, 2022 at 12:08 PM Catalin Marinas wrote: > > With kstrdup() modified to pass __GFP_PACKED (as per the last hunk in > the diff below), I get just after boot: > > kmalloc-128 8966 9056 128 32 > kmalloc-96 0 0 96 42 > kmalloc-64 192 192 64 64 > kmalloc-32 768 768 32 128 > kmalloc-16 2048 2048 16 256 > kmalloc-8 2560 2560 8 512 > > So that's probably the simplest approach and using the ftrace histogram > we can add the flag to more places. I agree that this seems to be the safest thing to do, and maybe __GFP_PACKED is a better flag name than __GFP_NODMA. That said, It worries me a bit in that to me "PACKED" implies "no alignment at all". And I could _easily_ see people still wanting to do 8-byte allocations that have 8-byte alignment because it's some kind of private pointer thing or whatever. For "kstrdup()", a flag like __GFP_PACKED makes 100% sense, since it literally wants byte alignment. But what about those "random small structures" cases? Anyway, I'm perfectly happy calling it __GFP_PACKED, but at a minimum document that "packed" in this case still means "__alignof__(unsigned long long)" or something like that? Linus