lkml.org 
[lkml]   [2023]   [Aug]   [16]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH bpf-next v4] selftests/bpf: trace_helpers.c: optimize kallsyms cache
From
Date
On 8/16/23 3:36 AM, Rong Tao wrote:
> From: Rong Tao <rongtao@cestc.cn>
>
> Static ksyms often have problems because the number of symbols exceeds the
> MAX_SYMS limit. Like changing the MAX_SYMS from 300000 to 400000 in
> commit e76a014334a6("selftests/bpf: Bump and validate MAX_SYMS") solves
> the problem somewhat, but it's not the perfect way.
>
> This commit uses dynamic memory allocation, which completely solves the
> problem caused by the limitation of the number of kallsyms.
>
> Acked-by: Stanislav Fomichev <sdf@google.com>
> Signed-off-by: Rong Tao <rongtao@cestc.cn>
> ---
> v4: Make sure most cases we don't need the realloc() path to begin with,
> and check strdup() return value.
> v3: https://lore.kernel.org/lkml/tencent_50B4B2622FE7546A5FF9464310650C008509@qq.com/
> Do not use structs and judge ksyms__add_symbol function return value.
> v2: https://lore.kernel.org/lkml/tencent_B655EE5E5D463110D70CD2846AB3262EED09@qq.com/
> Do the usual len/capacity scheme here to amortize the cost of realloc, and
> don't free symbols.
> v1: https://lore.kernel.org/lkml/tencent_AB461510B10CD484E0B2F62E3754165F2909@qq.com/
> ---
> tools/testing/selftests/bpf/trace_helpers.c | 46 ++++++++++++++++-----
> 1 file changed, 36 insertions(+), 10 deletions(-)
>
> diff --git a/tools/testing/selftests/bpf/trace_helpers.c b/tools/testing/selftests/bpf/trace_helpers.c
> index f83d9f65c65b..a1461508925e 100644
> --- a/tools/testing/selftests/bpf/trace_helpers.c
> +++ b/tools/testing/selftests/bpf/trace_helpers.c
> @@ -18,10 +18,35 @@
> #define TRACEFS_PIPE "/sys/kernel/tracing/trace_pipe"
> #define DEBUGFS_PIPE "/sys/kernel/debug/tracing/trace_pipe"
>
> -#define MAX_SYMS 400000
> -static struct ksym syms[MAX_SYMS];
> +static struct ksym *syms;
> +static int sym_cap;
> static int sym_cnt;
>
> +static int ksyms__add_symbol(const char *name, unsigned long addr)
> +{
> + void *tmp;
> + unsigned int new_cap;
> +
> + if (sym_cnt + 1 > sym_cap) {
> + new_cap = sym_cap * 4 / 3;
> + tmp = realloc(syms, sizeof(struct ksym) * new_cap);
> + if (!tmp)
> + return -ENOMEM;
> + syms = tmp;
> + sym_cap = new_cap;
> + }
> +
> + tmp = strdup(name);
> + if (!tmp)
> + return -ENOMEM;
> + syms[sym_cnt].addr = addr;
> + syms[sym_cnt].name = tmp;
> +
> + sym_cnt++;
> +
> + return 0;
> +}

Since this patch is about improving the load_kallsyms_refresh(), I mentioned in the v3
that it would also be good to have the counterpart to release the allocated memory once
the test concluded or upon error given it's dynamically allocated.

> static int ksym_cmp(const void *p1, const void *p2)
> {
> return ((struct ksym *)p1)->addr - ((struct ksym *)p2)->addr;
> @@ -33,9 +58,14 @@ int load_kallsyms_refresh(void)
> char func[256], buf[256];
> char symbol;
> void *addr;
> - int i = 0;
> + int ret;
>
> + /* Make sure most cases we don't need the realloc() path to begin with */
> + sym_cap = 400000;
> sym_cnt = 0;
> + syms = malloc(sizeof(struct ksym) * sym_cap);
> + if (!syms)
> + return -ENOMEM;
>
> f = fopen("/proc/kallsyms", "r");
> if (!f)
> @@ -46,15 +76,11 @@ int load_kallsyms_refresh(void)
> break;
> if (!addr)
> continue;
> - if (i >= MAX_SYMS)
> - return -EFBIG;
> -
> - syms[i].addr = (long) addr;
> - syms[i].name = strdup(func);
> - i++;
> + ret = ksyms__add_symbol(func, (unsigned long)addr);
> + if (ret)
> + return ret;
> }
> fclose(f);
> - sym_cnt = i;
> qsort(syms, sym_cnt, sizeof(struct ksym), ksym_cmp);
> return 0;
> }
>

Thanks,
Daniel

\
 
 \ /
  Last update: 2023-08-16 19:01    [W:0.046 / U:0.012 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site