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Using per-cpu thread pool we can reduce the scheduling latency compared to workqueue implementation. With this patch scheduling latency and variation is reduced as per-cpu threads are high priority kthread_workers. The results were evaluated on arm64 Android devices running 5.10 kernel. The table below shows resulting improvements of total scheduling latency for the same app launch benchmark runs with 50 iterations. Scheduling latency is the latency between when the task (workqueue kworker vs kthread_worker) became eligible to run to when it actually started running. +-------------------------+-----------+----------------+---------+ | | workqueue | kthread_worker | diff | +-------------------------+-----------+----------------+---------+ | Average (us) | 15253 | 2914 | -80.89% | | Median (us) | 14001 | 2912 | -79.20% | | Minimum (us) | 3117 | 1027 | -67.05% | | Maximum (us) | 30170 | 3805 | -87.39% | | Standard deviation (us) | 7166 | 359 | | +-------------------------+-----------+----------------+---------+ Background: Boot times and cold app launch benchmarks are very important to the Android ecosystem as they directly translate to responsiveness from user point of view. While EROFS provides a lot of important features like space savings, we saw some performance penalty in cold app launch benchmarks in few scenarios. Analysis showed that the significant variance was coming from the scheduling cost while decompression cost was more or less the same. Having per-cpu thread pool we can see from the above table that this variation is reduced by ~80% on average. This problem was discussed at LPC 2022. Link to LPC 2022 slides and talk at [1] [1] https://lpc.events/event/16/contributions/1338/ [ Gao Xiang: At least, we have to add this until WQ_UNBOUND workqueue issue [2] on many arm64 devices is resolved. ] [2] https://lore.kernel.org/r/CAJkfWY490-m6wNubkxiTPsW59sfsQs37Wey279LmiRxKt7aQYg@mail.gmail.com Signed-off-by: Sandeep Dhavale <dhavale@google.com> Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com> Link: https://lore.kernel.org/r/20230208093322.75816-1-hsiangkao@linux.alibaba.com
128 lines
4 KiB
Text
128 lines
4 KiB
Text
# SPDX-License-Identifier: GPL-2.0-only
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config EROFS_FS
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tristate "EROFS filesystem support"
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depends on BLOCK
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select FS_IOMAP
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select LIBCRC32C
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help
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EROFS (Enhanced Read-Only File System) is a lightweight read-only
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file system with modern designs (e.g. no buffer heads, inline
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xattrs/data, chunk-based deduplication, multiple devices, etc.) for
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scenarios which need high-performance read-only solutions, e.g.
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smartphones with Android OS, LiveCDs and high-density hosts with
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numerous containers;
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It also provides fixed-sized output compression support in order to
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improve storage density as well as keep relatively higher compression
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ratios and implements in-place decompression to reuse the file page
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for compressed data temporarily with proper strategies, which is
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quite useful to ensure guaranteed end-to-end runtime decompression
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performance under extremely memory pressure without extra cost.
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See the documentation at <file:Documentation/filesystems/erofs.rst>
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for more details.
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If unsure, say N.
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config EROFS_FS_DEBUG
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bool "EROFS debugging feature"
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depends on EROFS_FS
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help
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Print debugging messages and enable more BUG_ONs which check
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filesystem consistency and find potential issues aggressively,
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which can be used for Android eng build, for example.
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For daily use, say N.
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config EROFS_FS_XATTR
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bool "EROFS extended attributes"
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depends on EROFS_FS
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default y
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help
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Extended attributes are name:value pairs associated with inodes by
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the kernel or by users (see the attr(5) manual page, or visit
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<http://acl.bestbits.at/> for details).
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If unsure, say N.
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config EROFS_FS_POSIX_ACL
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bool "EROFS Access Control Lists"
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depends on EROFS_FS_XATTR
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select FS_POSIX_ACL
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default y
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help
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Posix Access Control Lists (ACLs) support permissions for users and
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groups beyond the owner/group/world scheme.
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To learn more about Access Control Lists, visit the POSIX ACLs for
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Linux website <http://acl.bestbits.at/>.
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If you don't know what Access Control Lists are, say N.
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config EROFS_FS_SECURITY
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bool "EROFS Security Labels"
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depends on EROFS_FS_XATTR
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default y
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help
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Security labels provide an access control facility to support Linux
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Security Models (LSMs) accepted by AppArmor, SELinux, Smack and TOMOYO
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Linux. This option enables an extended attribute handler for file
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security labels in the erofs filesystem, so that it requires enabling
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the extended attribute support in advance.
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If you are not using a security module, say N.
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config EROFS_FS_ZIP
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bool "EROFS Data Compression Support"
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depends on EROFS_FS
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select LZ4_DECOMPRESS
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default y
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help
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Enable fixed-sized output compression for EROFS.
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If you don't want to enable compression feature, say N.
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config EROFS_FS_ZIP_LZMA
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bool "EROFS LZMA compressed data support"
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depends on EROFS_FS_ZIP
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select XZ_DEC
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select XZ_DEC_MICROLZMA
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help
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Saying Y here includes support for reading EROFS file systems
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containing LZMA compressed data, specifically called microLZMA. it
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gives better compression ratios than the LZ4 algorithm, at the
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expense of more CPU overhead.
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LZMA support is an experimental feature for now and so most file
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systems will be readable without selecting this option.
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If unsure, say N.
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config EROFS_FS_ONDEMAND
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bool "EROFS fscache-based on-demand read support"
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depends on CACHEFILES_ONDEMAND && (EROFS_FS=m && FSCACHE || EROFS_FS=y && FSCACHE=y)
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default n
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help
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This permits EROFS to use fscache-backed data blobs with on-demand
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read support.
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If unsure, say N.
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config EROFS_FS_PCPU_KTHREAD
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bool "EROFS per-cpu decompression kthread workers"
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depends on EROFS_FS_ZIP
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help
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Saying Y here enables per-CPU kthread workers pool to carry out
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async decompression for low latencies on some architectures.
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If unsure, say N.
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config EROFS_FS_PCPU_KTHREAD_HIPRI
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bool "EROFS high priority per-CPU kthread workers"
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depends on EROFS_FS_ZIP && EROFS_FS_PCPU_KTHREAD
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help
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This permits EROFS to configure per-CPU kthread workers to run
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at higher priority.
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If unsure, say N.
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