On Wed Aug 21, 2024 at 4:54 AM EEST, Haitao Huang wrote: > sgx_reclaim_direct() was introduced to preemptively reclaim some pages > as the best effort to avoid on-demand reclamation that can stall forward > progress in some situations, e.g., allocating pages to load previously > reclaimed page to perform EDMM operations on [1]. > > Currently when the global usage is close to the capacity, > sgx_reclaim_direct() makes one invocation to sgx_reclaim_pages_global() > but does not guarantee there are free pages available for later > allocations to succeed. In other words, the only goal here is to reduce > the chance of on-demand reclamation at allocation time. In cases of > allocation failure, the caller, the EDMM ioctl()'s, would return -EAGAIN > to user space and let the user space to decide whether to retry or not. > > With EPC cgroups enabled, usage of a cgroup can also reach its limit > (usually much lower than capacity) and trigger per-cgroup reclamation. > Implement a similar strategy to reduce the chance of on-demand > per-cgroup reclamation for this use case. > > Create a wrapper, sgx_cgroup_reclaim_direct(), to perform a preemptive > reclamation at cgroup level, and have sgx_reclaim_direct() call it when > EPC cgroup is enabled. > > [1] https://lore.kernel.org/all/a0d8f037c4a075d56bf79f432438412985f7ff7a.1652137848.git.reinette.chatre@xxxxxxxxx/T/#u > > Signed-off-by: Haitao Huang <haitao.huang@xxxxxxxxxxxxxxx> > --- > arch/x86/kernel/cpu/sgx/epc_cgroup.c | 15 +++++++++++++++ > arch/x86/kernel/cpu/sgx/epc_cgroup.h | 3 +++ > arch/x86/kernel/cpu/sgx/main.c | 4 ++++ > 3 files changed, 22 insertions(+) > > diff --git a/arch/x86/kernel/cpu/sgx/epc_cgroup.c b/arch/x86/kernel/cpu/sgx/epc_cgroup.c > index 23a61689e0d9..b7d60b2d878d 100644 > --- a/arch/x86/kernel/cpu/sgx/epc_cgroup.c > +++ b/arch/x86/kernel/cpu/sgx/epc_cgroup.c > @@ -252,6 +252,21 @@ void sgx_cgroup_reclaim_pages_global(struct mm_struct *charge_mm) > sgx_cgroup_reclaim_pages(&sgx_cg_root, charge_mm, SGX_NR_TO_SCAN); > } > > +/** > + * sgx_cgroup_reclaim_direct() - Preemptive reclamation. > + * > + * Scan and attempt to reclaim %SGX_NR_TO_SCAN as best effort to allow caller > + * make quick progress. > + */ > +void sgx_cgroup_reclaim_direct(void) > +{ > + struct sgx_cgroup *sgx_cg = sgx_get_current_cg(); > + > + if (sgx_cgroup_should_reclaim(sgx_cg)) > + sgx_cgroup_reclaim_pages(sgx_cg, current->mm, SGX_NR_TO_SCAN); > + sgx_put_cg(sgx_cg); > +} > + > /* > * Asynchronous work flow to reclaim pages from the cgroup when the cgroup is > * at/near its maximum capacity. > diff --git a/arch/x86/kernel/cpu/sgx/epc_cgroup.h b/arch/x86/kernel/cpu/sgx/epc_cgroup.h > index c0390111e28c..cf2b946d993e 100644 > --- a/arch/x86/kernel/cpu/sgx/epc_cgroup.h > +++ b/arch/x86/kernel/cpu/sgx/epc_cgroup.h > @@ -38,6 +38,8 @@ static inline void __init sgx_cgroup_register(void) { } > > static inline void sgx_cgroup_reclaim_pages_global(struct mm_struct *charge_mm) { } > > +static inline void sgx_cgroup_reclaim_direct(void) { } > + > #else /* CONFIG_CGROUP_MISC */ > > struct sgx_cgroup { > @@ -90,6 +92,7 @@ static inline void sgx_put_cg(struct sgx_cgroup *sgx_cg) > int sgx_cgroup_try_charge(struct sgx_cgroup *sgx_cg, enum sgx_reclaim reclaim); > void sgx_cgroup_uncharge(struct sgx_cgroup *sgx_cg); > void sgx_cgroup_reclaim_pages_global(struct mm_struct *charge_mm); > +void sgx_cgroup_reclaim_direct(void); > int __init sgx_cgroup_init(void); > void __init sgx_cgroup_register(void); > void __init sgx_cgroup_deinit(void); > diff --git a/arch/x86/kernel/cpu/sgx/main.c b/arch/x86/kernel/cpu/sgx/main.c > index d00cb012838b..9a8f91ebd21b 100644 > --- a/arch/x86/kernel/cpu/sgx/main.c > +++ b/arch/x86/kernel/cpu/sgx/main.c > @@ -428,6 +428,10 @@ static void sgx_reclaim_pages_global(struct mm_struct *charge_mm) > */ > void sgx_reclaim_direct(void) > { > + /* Reduce chance of per-cgroup reclamation for later allocation */ > + sgx_cgroup_reclaim_direct(); > + > + /* Reduce chance of the global reclamation for later allocation */ > if (sgx_should_reclaim_global(SGX_NR_LOW_PAGES)) > sgx_reclaim_pages_global(current->mm); > } Reviewed-by: Jarkko Sakkinen <jarkko@xxxxxxxxxx> BR, Jarkko
