On Tue, 6 Apr 2021, Sean Christopherson wrote: > Use GFP_KERNEL_ACCOUNT when allocating vCPUs to make it more obvious that > that the allocations are accounted, to make it easier to audit KVM's > allocations in the future, and to be consistent with other cache usage in > KVM. > > When using SLAB/SLUB, this is a nop as the cache itself is created with > SLAB_ACCOUNT. > > When using SLOB, there are caveats within caveats. SLOB doesn't honor > SLAB_ACCOUNT, so passing GFP_KERNEL_ACCOUNT will result in vCPU > allocations now being accounted. But, even that depends on internal > SLOB details as SLOB will only go to the page allocator when its cache is > depleted. That just happens to be extremely likely for vCPUs because the > size of kvm_vcpu is larger than the a page for almost all combinations of > architecture and page size. Whether or not the SLOB behavior is by > design is unknown; it's just as likely that no SLOB users care about > accounding and so no one has bothered to implemented support in SLOB. > Regardless, accounting vCPU allocations will not break SLOB+KVM+cgroup > users, if any exist. > > Cc: Wanpeng Li <kernellwp@xxxxxxxxx> > Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx> Always happy to see this ambiguity (SLAB_ACCOUNT vs GFP_KERNEL_ACCOUNT) resolved for slab allocations. Acked-by: David Rientjes <rientjes@xxxxxxxxxx>
