From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from mail-yb1-xb4a.google.com ([2607:f8b0:4864:20::b4a]) by bombadil.infradead.org with esmtps (Exim 4.96 #2 (Red Hat Linux)) id 1qLMXU-003sK5-2C for linux-arm-kernel@lists.infradead.org; Mon, 17 Jul 2023 11:38:05 +0000 Received: by mail-yb1-xb4a.google.com with SMTP id 3f1490d57ef6-c361777c7f7so8610937276.0 for ; Mon, 17 Jul 2023 04:37:14 -0700 (PDT) Date: Mon, 17 Jul 2023 13:37:03 +0200 Mime-Version: 1.0 Message-ID: <20230717113709.328671-1-glider@google.com> Subject: [PATCH v3 0/5] Implement MTE tag compression for swapped pages From: Alexander Potapenko List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+lwn-linux-arm-kernel=archive.lwn.net@lists.infradead.org List-Archive: To: glider@google.com, catalin.marinas@arm.com, will@kernel.org, pcc@google.com, andreyknvl@gmail.com, andriy.shevchenko@linux.intel.com, linux@rasmusvillemoes.dk, yury.norov@gmail.com Cc: linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, eugenis@google.com, syednwaris@gmail.com, william.gray@linaro.org Currently, when MTE pages are swapped out, the tags are kept in the memory, occupying 128 bytes per page. This is especially problematic for devices that use zram-backed in-memory swap, because tags stored uncompressed in the heap effectively reduce the available amount of swap memory. The RLE-based EA0 algorithm suggested by Evgenii Stepanov and implemented in this patch series is able to efficiently compress 128-byte tag buffers, resulting in practical compression ratio between 2.5x and 20x. In most cases it is possible to store the compressed data in 63-bit Xarray values, resulting in no extra memory allocations. Our measurements show that EA0 provides better compression than existing kernel compression algorithms (LZ4, LZO, LZ4HC, ZSTD) can offer, because EA0 specifically targets 128-byte buffers. To implement compression/decompression, we also extend with methods to set/get bit values at arbitrary places in the map. We refactor arch/arm64/mm/mteswap.c to support both the compressed (CONFIG_ARM64_MTE_COMP) and non-compressed case. For the former, in addition to tag compression, we move tag allocation from kmalloc() to separate kmem caches, providing greater locality and relaxing the alignment requirements. v3: - as suggested by Andy Shevchenko, use bitmap_get_value()/bitmap_set_value() written by Syed Nayyar Waris - switched to unsigned long to reduce typecasts - simplified the compression code v2: - as suggested by Yuri Norov, replace the poorly implemented struct bitq with Alexander Potapenko (5): lib/bitmap: add bitmap_{set,get}_value() lib/test_bitmap: add tests for bitmap_{set,get}_value() arm64: mte: implement CONFIG_ARM64_MTE_COMP arm64: mte: add a test for MTE tags compression arm64: mte: add compression support to mteswap.c arch/arm64/Kconfig | 20 ++ arch/arm64/include/asm/mtecomp.h | 60 +++++ arch/arm64/mm/Makefile | 7 + arch/arm64/mm/mtecomp.c | 406 +++++++++++++++++++++++++++++++ arch/arm64/mm/mteswap.c | 20 +- arch/arm64/mm/mteswap.h | 12 + arch/arm64/mm/mteswap_comp.c | 52 ++++ arch/arm64/mm/mteswap_nocomp.c | 38 +++ arch/arm64/mm/test_mtecomp.c | 177 ++++++++++++++ include/linux/bitmap.h | 57 +++++ lib/test_bitmap.c | 33 +++ 11 files changed, 871 insertions(+), 11 deletions(-) create mode 100644 arch/arm64/include/asm/mtecomp.h create mode 100644 arch/arm64/mm/mtecomp.c create mode 100644 arch/arm64/mm/mteswap.h create mode 100644 arch/arm64/mm/mteswap_comp.c create mode 100644 arch/arm64/mm/mteswap_nocomp.c create mode 100644 arch/arm64/mm/test_mtecomp.c -- 2.41.0.255.g8b1d071c50-goog _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel