Re: [PATCH v2 2/3] KVM: x86/mmu: Use MMU shrinker to shrink KVM MMU memory caches

[Vipin Sharma]

On Fri, Oct 4, 2024 at 12:55 PM Vipin Sharma <vipinsh@xxxxxxxxxx> wrote:
>
> Use MMU shrinker to iterate through all the vCPUs of all the VMs and
> free pages allocated in MMU memory caches. Protect cache allocation in
> page fault and MMU load path from MMU shrinker by using a per vCPU
> mutex. In MMU shrinker, move the iterated VM to the end of the VMs list
> so that the pain of emptying cache spread among other VMs too.
>
> The specific caches to empty are mmu_shadow_page_cache and
> mmu_shadowed_info_cache as these caches store whole pages. Emptying them
> will give more impact to shrinker compared to other caches like
> mmu_pte_list_desc_cache{} and mmu_page_header_cache{}
>
> Holding per vCPU mutex lock ensures that a vCPU doesn't get surprised
> by finding its cache emptied after filling them up for page table
> allocations during page fault handling and MMU load operation. Per vCPU
> mutex also makes sure there is only race between MMU shrinker and all
> other vCPUs. This should result in very less contention.
>
> Signed-off-by: Vipin Sharma <vipinsh@xxxxxxxxxx>

I also meant to add
Suggested-by: Sean Christopherson <seanjc@xxxxxxxxxx>
Suggested-by: David Matlack <dmatlack@xxxxxxxxxx>

I can send v3 or please take it from v2.