From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-lj1-f169.google.com (mail-lj1-f169.google.com [209.85.208.169]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A463EC2E9 for ; Sat, 3 Jun 2023 21:12:04 +0000 (UTC) Received: by mail-lj1-f169.google.com with SMTP id 38308e7fff4ca-2b1afe57bdfso23747721fa.0 for ; Sat, 03 Jun 2023 14:12:04 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20221208; t=1685826722; x=1688418722; h=content-transfer-encoding:cc:to:subject:message-id:date:from :in-reply-to:references:mime-version:from:to:cc:subject:date :message-id:reply-to; bh=ywQUs5Fiz0nF2jpbvNI9hUxAw7fBwSlpxtNbhNWOdKQ=; b=RDS3HF6Dzg4udc+gzR1ge+A8FipEjdhBSdULq7dQD2UyV6dgjBvuZgGerD6vUs2YSm VDnqI9KNtr2Dk7Dcagvb3z7MHB6yFn9dZVHE0avEHhNOnZSxu+haoNYcH+DbvcdZqhp2 V/2FcSs+Og/LSo+4chvosoksvs7WCJCCw38bmEWjYWWbCKP1NNCl8K5ura9Sf0w8P5PP 7V+264OxyeQzdq0h0Oa1oSNUiGbjJiqkYN3172ascXs+vGBmB8K0oc564ajmaECysFRA O+qDRdpmwpV7013SWgjBPZmxYgAbk4/aYxoKzE2wIVyrPNGanFSOTGWVNORuh+LwDAsi f1HQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1685826722; x=1688418722; h=content-transfer-encoding:cc:to:subject:message-id:date:from :in-reply-to:references:mime-version:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=ywQUs5Fiz0nF2jpbvNI9hUxAw7fBwSlpxtNbhNWOdKQ=; b=Yyv9LQ+30zv2OYMBd5cgSNYqNegrldUpqSkoUreIjSmpqaGQr5ZGEZA3ctjrc/TZ+/ P5fMQ9OlSZpsxNmGcgntw2p3eOiXZtZSiBautIMdSiEU/PJUBDtY8+c2MmveRHCoM10h NfBb7MMSaxS8EyQ+LEJtEzgzsjewj+WtN3bko30OVBQHlWwX7a2k9124z+YxwTAZuvk/ G3P2xako3ZIlFck8DeRyVdq2AnWytUw4FMF3Ik2B6rFWBDX9kyNNi/LUOszZaM5W9156 OZCW6I6TGBPtu/Ib7ZVnKeAD1wR0G/nqzBQIjXEXdxt7Ue8Sb2wcM+xLfY+r0URXERK6 korQ== X-Gm-Message-State: AC+VfDz7/WnhuGT2Ouec4REwwy8wTxHGi4kvJTILbro8tEg6OMJlz1Z4 oUpOzXvGv7mUMW3zFHQptnys8RJusvr8NEU4Qw0= X-Google-Smtp-Source: ACHHUZ7QpjsIySl/XiT4DfbanAj3JM5KVAqgA/T1nohoUOzVT96eBA8GwqXTmRgv+kLRpCQJ8cFP5VM7V3QLXDceJ3I= X-Received: by 2002:a2e:88d6:0:b0:2a7:b986:3481 with SMTP id a22-20020a2e88d6000000b002a7b9863481mr1909233ljk.41.1685826722179; Sat, 03 Jun 2023 14:12:02 -0700 (PDT) Precedence: bulk X-Mailing-List: loongarch@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 References: <20230601101257.530867-1-rppt@kernel.org> In-Reply-To: From: Puranjay Mohan Date: Sat, 3 Jun 2023 23:11:51 +0200 Message-ID: Subject: Re: [PATCH 00/13] mm: jit/text allocator To: Song Liu Cc: Mark Rutland , Kent Overstreet , Mike Rapoport , linux-kernel@vger.kernel.org, Andrew Morton , Catalin Marinas , Christophe Leroy , "David S. Miller" , Dinh Nguyen , Heiko Carstens , Helge Deller , Huacai Chen , Luis Chamberlain , Michael Ellerman , "Naveen N. Rao" , Palmer Dabbelt , Russell King , Steven Rostedt , Thomas Bogendoerfer , Thomas Gleixner , Will Deacon , bpf@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-mips@vger.kernel.org, linux-mm@kvack.org, linux-modules@vger.kernel.org, linux-parisc@vger.kernel.org, linux-riscv@lists.infradead.org, linux-s390@vger.kernel.org, linux-trace-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, loongarch@lists.linux.dev, netdev@vger.kernel.org, sparclinux@vger.kernel.org, x86@kernel.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Fri, Jun 2, 2023 at 8:21=E2=80=AFPM Song Liu wrote: > > On Fri, Jun 2, 2023 at 2:35=E2=80=AFAM Mark Rutland wrote: > > > > On Thu, Jun 01, 2023 at 02:14:56PM -0400, Kent Overstreet wrote: > > > On Thu, Jun 01, 2023 at 05:12:03PM +0100, Mark Rutland wrote: > > > > For a while I have wanted to give kprobes its own allocator so that= it can work > > > > even with CONFIG_MODULES=3Dn, and so that it doesn't have to waste = VA space in > > > > the modules area. > > > > > > > > Given that, I think these should have their own allocator functions= that can be > > > > provided independently, even if those happen to use common infrastr= ucture. > > > > > > How much memory can kprobes conceivably use? I think we also want to = try > > > to push back on combinatorial new allocators, if we can. > > > > That depends on who's using it, and how (e.g. via BPF). > > > > To be clear, I'm not necessarily asking for entirely different allocato= rs, but > > I do thinkg that we want wrappers that can at least pass distinct start= +end > > parameters to a common allocator, and for arm64's modules code I'd expe= ct that > > we'd keep the range falblack logic out of the common allcoator, and jus= t call > > it twice. > > > > > > > Several architectures override module_alloc() because of various > > > > > constraints where the executable memory can be located and this c= auses > > > > > additional obstacles for improvements of code allocation. > > > > > > > > > > This set splits code allocation from modules by introducing > > > > > jit_text_alloc(), jit_data_alloc() and jit_free() APIs, replaces = call > > > > > sites of module_alloc() and module_memfree() with the new APIs an= d > > > > > implements core text and related allocation in a central place. > > > > > > > > > > Instead of architecture specific overrides for module_alloc(), th= e > > > > > architectures that require non-default behaviour for text allocat= ion must > > > > > fill jit_alloc_params structure and implement jit_alloc_arch_para= ms() that > > > > > returns a pointer to that structure. If an architecture does not = implement > > > > > jit_alloc_arch_params(), the defaults compatible with the current > > > > > modules::module_alloc() are used. > > > > > > > > As above, I suspect that each of the callsites should probably be u= sing common > > > > infrastructure, but I don't think that a single jit_alloc_arch_para= ms() makes > > > > sense, since the parameters for each case may need to be distinct. > > > > > > I don't see how that follows. The whole point of function parameters = is > > > that they may be different :) > > > > What I mean is that jit_alloc_arch_params() tries to aggregate common > > parameters, but they aren't actually common (e.g. the actual start+end = range > > for allocation). > > > > > Can you give more detail on what parameters you need? If the only ext= ra > > > parameter is just "does this allocation need to live close to kernel > > > text", that's not that big of a deal. > > > > My thinking was that we at least need the start + end for each caller. = That > > might be it, tbh. > > IIUC, arm64 uses VMALLOC address space for BPF programs. The reason > is each BPF program uses at least 64kB (one page) out of the 128MB > address space. Puranjay Mohan (CC'ed) is working on enabling > bpf_prog_pack for arm64. Once this work is done, multiple BPF programs > will be able to share a page. Will this improvement remove the need to > specify a different address range for BPF programs? Hi, Thanks for adding me to the conversation. The ARM64 BPF JIT used to allocate the memory using module_alloc but it was not optimal because BPF programs and modules were sharing the 128 MB module region. This was fixed by 91fc957c9b1d ("arm64/bpf: don't allocate BPF JIT programs in module memory"= ) It created a dedicated 128 MB region set aside for BPF programs. But 128MB could get exhausted especially where PAGE_SIZE is 64KB - one page is needed per program. This restriction was removed by b89ddf4cca43 ("arm64/bpf: Remove 128MB limit for BPF JIT programs") So, currently BPF programs are using a full page from vmalloc (4 KB, 16 KB, or 64 KB). This wastes memory and also causes iTLB pressure. Enabling bpf_prog_pack for ARM64 would fix it. I am doing some final tests and will send the patch= es in 1-2 days. 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charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Mailman-Approved-At: Sun, 04 Jun 2023 08:34:39 +1000 X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Mark Rutland , x86@kernel.org, Catalin Marinas , linux-mips@vger.kernel.org, linux-mm@kvack.org, sparclinux@vger.kernel.org, linux-riscv@lists.infradead.org, Will Deacon , linux-s390@vger.kernel.org, Helge Deller , Huacai Chen , Russell King , "Naveen N. Rao" , linux-trace-kernel@vger.kernel.org, Heiko Carstens , Steven Rostedt , loongarch@lists.linux.dev, Thomas Gleixner , Andrew Morton , linux-arm-kernel@lists.infradead.org, Thomas Bogendoerfer , linux-parisc@vger.kernel.org, netdev@vger.kernel.org, Kent Overstreet , linux-kernel@vger.kernel.org, Dinh Nguyen , Luis Chamberlain , Palmer Dabbelt , linux-modules@vger.kernel.org, bpf@ vger.kernel.org, linuxppc-dev@lists.ozlabs.org, "David S. Miller" , Mike Rapoport Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On Fri, Jun 2, 2023 at 8:21=E2=80=AFPM Song Liu wrote: > > On Fri, Jun 2, 2023 at 2:35=E2=80=AFAM Mark Rutland wrote: > > > > On Thu, Jun 01, 2023 at 02:14:56PM -0400, Kent Overstreet wrote: > > > On Thu, Jun 01, 2023 at 05:12:03PM +0100, Mark Rutland wrote: > > > > For a while I have wanted to give kprobes its own allocator so that= it can work > > > > even with CONFIG_MODULES=3Dn, and so that it doesn't have to waste = VA space in > > > > the modules area. > > > > > > > > Given that, I think these should have their own allocator functions= that can be > > > > provided independently, even if those happen to use common infrastr= ucture. > > > > > > How much memory can kprobes conceivably use? I think we also want to = try > > > to push back on combinatorial new allocators, if we can. > > > > That depends on who's using it, and how (e.g. via BPF). > > > > To be clear, I'm not necessarily asking for entirely different allocato= rs, but > > I do thinkg that we want wrappers that can at least pass distinct start= +end > > parameters to a common allocator, and for arm64's modules code I'd expe= ct that > > we'd keep the range falblack logic out of the common allcoator, and jus= t call > > it twice. > > > > > > > Several architectures override module_alloc() because of various > > > > > constraints where the executable memory can be located and this c= auses > > > > > additional obstacles for improvements of code allocation. > > > > > > > > > > This set splits code allocation from modules by introducing > > > > > jit_text_alloc(), jit_data_alloc() and jit_free() APIs, replaces = call > > > > > sites of module_alloc() and module_memfree() with the new APIs an= d > > > > > implements core text and related allocation in a central place. > > > > > > > > > > Instead of architecture specific overrides for module_alloc(), th= e > > > > > architectures that require non-default behaviour for text allocat= ion must > > > > > fill jit_alloc_params structure and implement jit_alloc_arch_para= ms() that > > > > > returns a pointer to that structure. If an architecture does not = implement > > > > > jit_alloc_arch_params(), the defaults compatible with the current > > > > > modules::module_alloc() are used. > > > > > > > > As above, I suspect that each of the callsites should probably be u= sing common > > > > infrastructure, but I don't think that a single jit_alloc_arch_para= ms() makes > > > > sense, since the parameters for each case may need to be distinct. > > > > > > I don't see how that follows. The whole point of function parameters = is > > > that they may be different :) > > > > What I mean is that jit_alloc_arch_params() tries to aggregate common > > parameters, but they aren't actually common (e.g. the actual start+end = range > > for allocation). > > > > > Can you give more detail on what parameters you need? If the only ext= ra > > > parameter is just "does this allocation need to live close to kernel > > > text", that's not that big of a deal. > > > > My thinking was that we at least need the start + end for each caller. = That > > might be it, tbh. > > IIUC, arm64 uses VMALLOC address space for BPF programs. The reason > is each BPF program uses at least 64kB (one page) out of the 128MB > address space. Puranjay Mohan (CC'ed) is working on enabling > bpf_prog_pack for arm64. Once this work is done, multiple BPF programs > will be able to share a page. Will this improvement remove the need to > specify a different address range for BPF programs? Hi, Thanks for adding me to the conversation. The ARM64 BPF JIT used to allocate the memory using module_alloc but it was not optimal because BPF programs and modules were sharing the 128 MB module region. This was fixed by 91fc957c9b1d ("arm64/bpf: don't allocate BPF JIT programs in module memory"= ) It created a dedicated 128 MB region set aside for BPF programs. But 128MB could get exhausted especially where PAGE_SIZE is 64KB - one page is needed per program. This restriction was removed by b89ddf4cca43 ("arm64/bpf: Remove 128MB limit for BPF JIT programs") So, currently BPF programs are using a full page from vmalloc (4 KB, 16 KB, or 64 KB). This wastes memory and also causes iTLB pressure. Enabling bpf_prog_pack for ARM64 would fix it. I am doing some final tests and will send the patch= es in 1-2 days. Thanks, Puranjay