Use dedicated SLABs

[l0kod]

Using a kmem_cache per Landlock's kernel type could improve performance, and it would also be useful to get some metrics via /proc/slabinfo.

One SLAB per:

• struct landlock_object
• struct landlock_rule
• struct landlock_ruleset
• struct landlock_hierarchy

[ayush-0110]

Hi, I am Ayush, an outreachy applicant. I have worked on several patches and got them reviewed as mentioned in project guidelines. I want to work on this issue. Can you please assign it to me and help me get started on the same?
@l0kod @AlisonSchofield

[l0kod]

Hi Ayush!

The idea is to replace kzalloc() calls with kmem_cache_zalloc() and update the related dependencies. You should find plenty of examples in the kernel code (e.g. lsm_file_cache).

However, struct landlock_ruleset would not work because it contains a flexible array member (FAM). With a separate patch series, we could leverage the upcoming kmem_buckets_alloc().

[l0kod]

I'm assigning this issue to you. Please regularly update it with your progress. This doesn't need to be long but just enough to make sure you are not blocked.

[ayush-0110]

Thanks a lot @l0kod . Will definitely keep updating progress and seek your guidance if anywhere I feel stuck.

[ayush-0110]

Hello @l0kod . I have gone through the lsm_file_cache code for reference and tried to use kmem_cache_zalloc( ) for struct landlock_object. Let me share the steps taken, kindly correct me wherever I am wrong:

1. created a struct of type kmem_cache to create cache.
2. created one initialization function to create cache to allocate memory from.
3. replaced zalloc calls with kmem_cache_zalloc( ).

the problem I am facing is: I am not getting where to call the initialisation function to ensure cache is created only once. could you help me please? @l0kod @AlisonSchofield

[l0kod]

Hello @l0kod . I have gone through the lsm_file_cache code for reference and tried to use kmem_cache_zalloc( ) for struct landlock_object. Let me share the steps taken, kindly correct me wherever I am wrong:

1. created a struct of type kmem_cache to create cache.
2. created one initialization function to create cache to allocate memory from.
3. replaced zalloc calls with kmem_cache_zalloc( ).

This looks good.

the problem I am facing is: I am not getting where to call the initialisation function to ensure cache is created only once. could you help me please? @l0kod @AlisonSchofield

You can call the initialization function from landlock_init().

[ayush-0110]

Okay. Thanks @l0kod . I am sending the changes for your review. Kindly look into them and instruct me further. Thanks.

[l0kod]

For reference: the related patch.

[ayush-0110]

Hello @l0kod.
I was trying to work on the suggestion of Paul and I am facing some problem regarding replacing kzalloc with
kmem_cache_zalloc calls when using KMEM macro from include/linux/slab.h because for
kmem_cache_zalloc I will be needing a cache pointer, but KMEM macro
doesn't return or allocate any such pointer. So is there any way to do this using macro or do i have to avoid using that macro for this case and use all methods regarding kmem as defined in the linux memory management API doc?

[ayush-0110]

Hello @l0kod . I sent a V2 of the patch. Could you please look into it and suggest me if any changes have to be done? Thanks

[ayush-0110]

Hello @l0kod @AlisonSchofield. I have created a complete patch aimed at solving this issue where I have used kmem to replace the kzalloc calls with kmem_cache_zalloc and also have metrics using /proc/slabinfo. Kindly look into it. Thanks
Link: the related patch

[ayush-0110]

Hello @l0kod @AlisonSchofield. Kindly look into the patch I created as today is the last date for submitting our final application.

[l0kod]

Hello @l0kod @AlisonSchofield. Kindly look into the patch I created as today is the last date for submitting our final application.

You can use the link to the latest patch as contribution. I'll review it shortly.

[ayush-0110]

Ok @l0kod . Thanks. Now I wish to change the calls for struct landlock_ruleset as well and as you mentioned, i have to use kmem_buckets_alloc(). Can you guide me about how to proceed with it?

[l0kod]

It's too soon to work on kmem_buckets_alloc() because of the ongoing discussion. We'll see what happen.

As suggested in the mailing list, some metrics would be useful to know the impact of kmem_cache.

[ayush-0110]

Hello @l0kod. In my recent patch, I included some metrics from /proc/slabinfo, as that was mentioned in the issue. Any other metrics also needed for the same??

[l0kod]

Hello @l0kod. In my recent patch, I included some metrics from /proc/slabinfo, as that was mentioned in the issue. Any other metrics also needed for the same??

By metric I mean to measure the performance impact of such change. This should help: #24