mirror of
https://github.com/hanzoai/visor.git
synced 2026-09-24 17:04:14 +00:00
Ayush Ranjan
3358345b71
Regular file reads copy data out of the image's shared mapping. When the image is backed by slow storage such as a FUSE mount, walking the mapping faults it in one page at a time, turning a large read into many small, largely serialized requests to the FUSE server. This makes erofs much slower than fsimpl/gofer for large reads on such backends. On those filesystems, read the data directly from the image file descriptor with preadv2(2) instead, so the host serves a large read with a single syscall and its own readahead, matching how fsimpl/gofer reads from host FDs. The mapping copy is kept everywhere else, since it avoids a syscall and is faster when the page cache is warm. The backing filesystem is detected at mount time via fstatfs(2); currently only FUSE opts into FD reads. Inode.Data, which returned the data as a mapping-backed BlockSeq, is replaced by Inode.DataRanges, which returns the image byte ranges that hold the inode's data.
34 lines
670 B
Python
34 lines
670 B
Python
load("//tools:defs.bzl", "go_library", "go_test")
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package(
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default_applicable_licenses = ["//:license"],
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licenses = ["notice"],
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)
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go_library(
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name = "erofs",
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srcs = [
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"erofs.go",
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"erofs_unsafe.go",
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],
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marshal = True,
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visibility = ["//visibility:public"],
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deps = [
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"//pkg/abi/linux",
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"//pkg/cleanup",
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"//pkg/errors/linuxerr",
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"//pkg/gohacks",
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"//pkg/hostarch",
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"//pkg/log",
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"//pkg/marshal",
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"@org_golang_x_sys//unix:go_default_library",
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],
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)
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go_test(
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name = "erofs_test",
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size = "small",
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srcs = ["erofs_test.go"],
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library = ":erofs",
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)
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