On 2023/3/15 16:52, Marco Elver wrote:
On Wed, Mar 15, 2023 at 02:51PM +0800, Zhenhua Huang wrote:
[...]
Is it possible to free this early allocated memory later in
mm_init()->kfence_alloc_pool()? if that is not possible, can we think of
adding early param for kfence?
If we freed that buffer, there may be no chance to get that page granularity
mapped buffer again.. as all these allocation/free are through normal buddy
allocator.
At this stage, seems only additional early param can work.. Marco previously
wanted to reuse sample_interval but seems not doable now.
Hi Marco,
Sorry, Can we thought of the solution again? like
ARM64:
1. intercepts early boot arg and gives early alloc memory to KFENCE
2. KFENCE to disable dynamic switch
3. disable page gran and save memory overhead
The purpose is in the case of w/o boot arg, it's just same as now.. arch
specific kfence buffer will not allocate. And w/ boot arg, we can get
expected saving.
You can get kfence.sample_interval with early_param(). mm/kfence/core.c
should be left as is with a module param, so it can be set at runtime in
/sys/modules/kfence/parameters/.
However you can add this to the #ifdef CONFIG_KFENCE in arm64 code
you're adding:
static bool kfence_early_init __initdata = !!CONFIG_KFENCE_SAMPLE_INTERVAL;
static int __init parse_kfence_early_init(char *p) {
int val;
if (get_option(&p, &val))
kfence_early_init = !!val;
return 0;
}
early_param("kfence.sample_interval", parse_kfence_early_init);
Nothing is preventing us from parsing kfence.sample_interval twice
during boot. At this stage you don't need the actual sample_interval,
only if kfence.sample_interval was provided on the cmdline and is not 0.
That will avoid adding another new param.
I'm fine with above solution, Thanks Marco. Let me make the patch and
share further.
Thanks,
Zhenhua
Thanks,
-- Marco
