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If we are accessing several times the modules and reading some sections by sucessive calls to the functions below, we are incurring in a penalty of having to open, parse the header and close the file. For each function. - kmod_module_get_info() - kmod_module_get_versions() - kmod_module_get_symbols() - kmod_module_get_dependency_symbols() These functions are particularly important to depmod. It calls all of them, for each module. Moreover there's a huge bottleneck in the open operation if we are using compression. Every time we open the module we need to uncompress the file and after getting the information we need we discard the result. This is clearly shown by profiling depmod with perf (record + report), using compressed modules: 64.07% depmod libz.so.1.2.7 [.] 0x00000000000074b8 ◆ 18.18% depmod libz.so.1.2.7 [.] crc32 ▒ 2.42% depmod libz.so.1.2.7 [.] inflate ▒ 1.17% depmod libc-2.16.so [.] __memcpy_ssse3_back ▒ 0.96% depmod [kernel.kallsyms] [k] copy_user_generic_string ▒ 0.89% depmod libc-2.16.so [.] __strcmp_sse42 ▒ 0.82% depmod [kernel.kallsyms] [k] hrtimer_interrupt ▒ 0.77% depmod libc-2.16.so [.] _int_malloc ▒ 0.44% depmod kmod-nolib [.] kmod_elf_get_strings ▒ 0.41% depmod kmod-nolib [.] kmod_elf_get_dependency_symbols ▒ 0.37% depmod kmod-nolib [.] kmod_elf_get_section ▒ 0.36% depmod kmod-nolib [.] kmod_elf_get_symbols ... Average of running depmod 5 times, dropping caches between them, in a slow spinning disk: Before: 12.25 +- 0.20 After: 8.20 +- 0.21 m-i-t: 9.62 +- 0.27 So this patch leads to an improvement of ~33% over unpatched version, ending up with 15% speedup over module-init-tools. |
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| .. | ||
| docs | ||
| .gitignore | ||
| COPYING | ||
| libkmod-array.c | ||
| libkmod-array.h | ||
| libkmod-config.c | ||
| libkmod-elf.c | ||
| libkmod-file.c | ||
| libkmod-hash.c | ||
| libkmod-hash.h | ||
| libkmod-index.c | ||
| libkmod-index.h | ||
| libkmod-list.c | ||
| libkmod-module.c | ||
| libkmod-private.h | ||
| libkmod-util.c | ||
| libkmod-util.h | ||
| libkmod.c | ||
| libkmod.h | ||
| libkmod.pc.in | ||
| libkmod.sym | ||
| macro.h | ||
| README | ||
libkmod - linux kernel module handling library
ABSTRACT
========
libkmod was created to allow programs to easily insert, remove and
list modules, also checking its properties, dependencies and aliases.
there is no shared/global context information and it can be used by
multiple sites on a single program, also being able to be used from
threads, although it's not thread safe (you must lock explicitly).
OVERVIEW
========
Every user should create and manage it's own library context with:
struct kmod_ctx *ctx = kmod_new(kernel_dirname);
kmod_unref(ctx);
Modules can be created with by various means:
struct kmod_module *mod;
int err;
err = kmod_module_new_from_path(ctx, path, &mod);
if (err < 0) {
/* code */
} else {
/* code */
kmod_module_unref(mod);
}
err = kmod_module_new_from_name(ctx, name, &mod);
if (err < 0) {
/* code */
} else {
/* code */
kmod_module_unref(mod);
}
Or could be resolved from a known alias to a list of alternatives:
struct kmod_list *list, *itr;
int err;
err = kmod_module_new_from_lookup(ctx, alias, &list);
if (err < 0) {
/* code */
} else {
kmod_list_foreach(itr, list) {
struct kmod_module *mod = kmod_module_get_module(itr);
/* code */
}
}