| Message ID | 20220920071317.1787-6-thunder.leizhen@huawei.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | kallsyms: Optimizes the performance of lookup symbols | expand |
On Tue 2022-09-20 15:13:14, Zhen Lei wrote: > Function kallsyms_on_each_symbol() traverses all symbols and submits each > symbol to the hook 'fn' for judgment and processing. For some cases, the > hook actually only handles the matched symbol, such as livepatch. > > So that, we can first compress the name being looked up and then use > it for comparison when traversing 'kallsyms_names', this greatly reduces > the time consumed by traversing. > > The pseudo code of the test case is as follows: > static int tst_find(void *data, const char *name, > struct module *mod, unsigned long addr) > { > if (strcmp(name, "vmap") == 0) > *(unsigned long *)data = addr; > return 0; > } > > static int tst_match(void *data, unsigned long addr) > { > *(unsigned long *)data = addr; > return 0; > } > > start = sched_clock(); > kallsyms_on_each_match_symbol(tst_match, "vmap", &addr); > end = sched_clock(); > > start = sched_clock(); > kallsyms_on_each_symbol(tst_find, &addr); > end = sched_clock(); > > The test results are as follows (twice): > kallsyms_on_each_match_symbol: 557400, 583900 > kallsyms_on_each_symbol : 16659500, 16113950 > > kallsyms_on_each_match_symbol() consumes only 3.48% of > kallsyms_on_each_symbol()'s time. > > --- a/kernel/kallsyms.c > +++ b/kernel/kallsyms.c > @@ -305,6 +305,31 @@ int kallsyms_on_each_symbol(int (*fn)(void *, const char *, struct module *, > return 0; > } > > +int kallsyms_on_each_match_symbol(int (*fn)(void *, unsigned long), > + const char *name, void *data) > +{ > + unsigned int i, off; > + int len, ret; > + char namebuf[KSYM_NAME_LEN]; > + > + len = kallsyms_name_to_tokens(name, namebuf); > + for (i = 0, off = 0; len && i < kallsyms_num_syms; i++) { > + if ((i & 0xfff) == 0) > + cond_resched(); > + > + if ((kallsyms_names[off] == len + 1) && > + !memcmp(&kallsyms_names[off + 2], namebuf, len)) { > + ret = fn(data, kallsyms_sym_address(i)); > + if (ret != 0) > + return ret; > + cond_resched(); > + } > + off += kallsyms_names[off] + 1; Similar tricky code is used also in kallsyms_lookup_name(). Please, avoid code duplication and put this into a helper funtion. Best Regards, Petr > + } > + > + return 0; > +} > + > static unsigned long get_symbol_pos(unsigned long addr, > unsigned long *symbolsize, > unsigned long *offset) > -- > 2.25.1
On 2022/9/21 23:30, Petr Mladek wrote: > On Tue 2022-09-20 15:13:14, Zhen Lei wrote: >> Function kallsyms_on_each_symbol() traverses all symbols and submits each >> symbol to the hook 'fn' for judgment and processing. For some cases, the >> hook actually only handles the matched symbol, such as livepatch. >> >> So that, we can first compress the name being looked up and then use >> it for comparison when traversing 'kallsyms_names', this greatly reduces >> the time consumed by traversing. >> >> The pseudo code of the test case is as follows: >> static int tst_find(void *data, const char *name, >> struct module *mod, unsigned long addr) >> { >> if (strcmp(name, "vmap") == 0) >> *(unsigned long *)data = addr; >> return 0; >> } >> >> static int tst_match(void *data, unsigned long addr) >> { >> *(unsigned long *)data = addr; >> return 0; >> } >> >> start = sched_clock(); >> kallsyms_on_each_match_symbol(tst_match, "vmap", &addr); >> end = sched_clock(); >> >> start = sched_clock(); >> kallsyms_on_each_symbol(tst_find, &addr); >> end = sched_clock(); >> >> The test results are as follows (twice): >> kallsyms_on_each_match_symbol: 557400, 583900 >> kallsyms_on_each_symbol : 16659500, 16113950 >> >> kallsyms_on_each_match_symbol() consumes only 3.48% of >> kallsyms_on_each_symbol()'s time. >> >> --- a/kernel/kallsyms.c >> +++ b/kernel/kallsyms.c >> @@ -305,6 +305,31 @@ int kallsyms_on_each_symbol(int (*fn)(void *, const char *, struct module *, >> return 0; >> } >> >> +int kallsyms_on_each_match_symbol(int (*fn)(void *, unsigned long), >> + const char *name, void *data) >> +{ >> + unsigned int i, off; >> + int len, ret; >> + char namebuf[KSYM_NAME_LEN]; >> + >> + len = kallsyms_name_to_tokens(name, namebuf); >> + for (i = 0, off = 0; len && i < kallsyms_num_syms; i++) { >> + if ((i & 0xfff) == 0) >> + cond_resched(); >> + >> + if ((kallsyms_names[off] == len + 1) && >> + !memcmp(&kallsyms_names[off + 2], namebuf, len)) { >> + ret = fn(data, kallsyms_sym_address(i)); >> + if (ret != 0) >> + return ret; >> + cond_resched(); >> + } >> + off += kallsyms_names[off] + 1; > > Similar tricky code is used also in kallsyms_lookup_name(). Please, > avoid code duplication and put this into a helper funtion. Okay, I'll try it. > > Best Regards, > Petr > >> + } >> + >> + return 0; >> +} >> + >> static unsigned long get_symbol_pos(unsigned long addr, >> unsigned long *symbolsize, >> unsigned long *offset) >> -- >> 2.25.1 > . >
diff --git a/include/linux/kallsyms.h b/include/linux/kallsyms.h index ad39636e0c3f122..f9f2cc084cab16b 100644 --- a/include/linux/kallsyms.h +++ b/include/linux/kallsyms.h @@ -69,6 +69,8 @@ static inline void *dereference_symbol_descriptor(void *ptr) int kallsyms_on_each_symbol(int (*fn)(void *, const char *, struct module *, unsigned long), void *data); +extern int kallsyms_on_each_match_symbol(int (*fn)(void *, unsigned long), + const char *name, void *data); /* Lookup the address for a symbol. Returns 0 if not found. */ unsigned long kallsyms_lookup_name(const char *name); @@ -168,6 +170,12 @@ static inline int kallsyms_on_each_symbol(int (*fn)(void *, const char *, struct { return -EOPNOTSUPP; } + +static inline int kallsyms_on_each_match_symbol(int (*fn)(void *, unsigned long), + const char *name, void *data) +{ + return -EOPNOTSUPP; +} #endif /*CONFIG_KALLSYMS*/ static inline void print_ip_sym(const char *loglvl, unsigned long ip) diff --git a/kernel/kallsyms.c b/kernel/kallsyms.c index 2d76196cfe89f34..cbcc9c560f5c188 100644 --- a/kernel/kallsyms.c +++ b/kernel/kallsyms.c @@ -305,6 +305,31 @@ int kallsyms_on_each_symbol(int (*fn)(void *, const char *, struct module *, return 0; } +int kallsyms_on_each_match_symbol(int (*fn)(void *, unsigned long), + const char *name, void *data) +{ + unsigned int i, off; + int len, ret; + char namebuf[KSYM_NAME_LEN]; + + len = kallsyms_name_to_tokens(name, namebuf); + for (i = 0, off = 0; len && i < kallsyms_num_syms; i++) { + if ((i & 0xfff) == 0) + cond_resched(); + + if ((kallsyms_names[off] == len + 1) && + !memcmp(&kallsyms_names[off + 2], namebuf, len)) { + ret = fn(data, kallsyms_sym_address(i)); + if (ret != 0) + return ret; + cond_resched(); + } + off += kallsyms_names[off] + 1; + } + + return 0; +} + static unsigned long get_symbol_pos(unsigned long addr, unsigned long *symbolsize, unsigned long *offset)
Function kallsyms_on_each_symbol() traverses all symbols and submits each symbol to the hook 'fn' for judgment and processing. For some cases, the hook actually only handles the matched symbol, such as livepatch. So that, we can first compress the name being looked up and then use it for comparison when traversing 'kallsyms_names', this greatly reduces the time consumed by traversing. The pseudo code of the test case is as follows: static int tst_find(void *data, const char *name, struct module *mod, unsigned long addr) { if (strcmp(name, "vmap") == 0) *(unsigned long *)data = addr; return 0; } static int tst_match(void *data, unsigned long addr) { *(unsigned long *)data = addr; return 0; } start = sched_clock(); kallsyms_on_each_match_symbol(tst_match, "vmap", &addr); end = sched_clock(); start = sched_clock(); kallsyms_on_each_symbol(tst_find, &addr); end = sched_clock(); The test results are as follows (twice): kallsyms_on_each_match_symbol: 557400, 583900 kallsyms_on_each_symbol : 16659500, 16113950 kallsyms_on_each_match_symbol() consumes only 3.48% of kallsyms_on_each_symbol()'s time. Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com> --- include/linux/kallsyms.h | 8 ++++++++ kernel/kallsyms.c | 25 +++++++++++++++++++++++++ 2 files changed, 33 insertions(+)