Re: [PATCH bpf-next v2 2/2] bpf: use realloc in bpf_patch_insn_data

[Anton Protopopov <a.s.protopopov@gmail.com>]

On 25/08/06 06:02PM, Eduard Zingerman wrote:
> Avoid excessive vzalloc/vfree calls when patching instructions in
> do_misc_fixups(). bpf_patch_insn_data() uses vzalloc to allocate new
> memory for env->insn_aux_data for each patch as follows:
> 
>   struct bpf_prog *bpf_patch_insn_data(env, ...)
>   {
>     ...
>     new_data = vzalloc(... O(program size) ...);
>     ...
>     adjust_insn_aux_data(env, new_data, ...);
>     ...
>   }
> 
>   void adjust_insn_aux_data(env, new_data, ...)
>   {
>     ...
>     memcpy(new_data, env->insn_aux_data);
>     vfree(env->insn_aux_data);
>     env->insn_aux_data = new_data;
>     ...
>   }
> 
> The vzalloc/vfree pair is hot in perf report collected for e.g.
> pyperf180 test case. It can be replaced with a call to vrealloc in
> order to reduce the number of actual memory allocations.

Given that I am in any case looking at the code around,
I've rebased on top of this change and tested it:

Tested-by: Anton Protopopov <a.s.protopopov@gmail.com>

> This is a stop-gap solution, as bpf_patch_insn_data is still hot in
> the profile. More comprehansive solutions had been discussed before
> e.g. as in [1].
> 
> [1] https://lore.kernel.org/bpf/CAEf4BzY_E8MSL4mD0UPuuiDcbJhh9e2xQo2=5w+ppRWWiYSGvQ@mail.gmail.com/
> 
> Suggested-by: Alexei Starovoitov <alexei.starovoitov@gmail.com>
> Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>

[snip]