With EPC cgroups, the global reclamation function,
sgx_reclaim_pages_global(), can no longer apply to the global LRU as
pages are now in per-cgroup LRUs.
Create a wrapper, sgx_cgroup_reclaim_global() to invoke
sgx_cgroup_reclaim_pages() passing in the root cgroup. Call this wrapper
from sgx_reclaim_pages_global() when cgroup is enabled. The wrapper will
scan and attempt to reclaim SGX_NR_TO_SCAN pages just like the current
global reclaim.
Note this simple implementation doesn't _exactly_ mimic the current
global EPC reclaim (which always tries to do the actual reclaim in batch
of SGX_NR_TO_SCAN pages): in rare cases when LRUs have less than
SGX_NR_TO_SCAN reclaimable pages, the actual reclaim of EPC pages will
be split into smaller batches _across_ multiple LRUs with each being
smaller than SGX_NR_TO_SCAN pages.
A more precise way to mimic the current global EPC reclaim would be to
have a new function to only "scan" (or "isolate") SGX_NR_TO_SCAN pages
_across_ the given EPC cgroup _AND_ its descendants, and then do the
actual reclaim in one batch. But this is unnecessarily complicated at
this stage to address such rare cases.
Signed-off-by: Haitao Huang <haitao.huang@xxxxxxxxxxxxxxx>
---
arch/x86/kernel/cpu/sgx/epc_cgroup.c | 12 ++++++++++++
arch/x86/kernel/cpu/sgx/epc_cgroup.h | 3 +++
arch/x86/kernel/cpu/sgx/main.c | 7 +++++++
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 ae65cac858f8..23a61689e0d9 100644
--- a/arch/x86/kernel/cpu/sgx/epc_cgroup.c
+++ b/arch/x86/kernel/cpu/sgx/epc_cgroup.c
@@ -240,6 +240,18 @@ static bool sgx_cgroup_should_reclaim(struct sgx_cgroup *sgx_cg)
return (cur >= max);
}
+/**
+ * sgx_cgroup_reclaim_pages_global() - Perform one round of global reclamation.
+ *
+ * @charge_mm: The mm to be charged for the backing store of reclaimed pages.
+ *
+ * Try to scan and attempt reclamation from root cgroup for %SGX_NR_TO_SCAN pages.
+ */
+void sgx_cgroup_reclaim_pages_global(struct mm_struct *charge_mm)
+{
+ sgx_cgroup_reclaim_pages(&sgx_cg_root, charge_mm, SGX_NR_TO_SCAN);
+}
+
/*
* 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 37364bdb797f..c0390111e28c 100644
--- a/arch/x86/kernel/cpu/sgx/epc_cgroup.h
+++ b/arch/x86/kernel/cpu/sgx/epc_cgroup.h
@@ -36,6 +36,8 @@ static inline void __init sgx_cgroup_deinit(void) { }
static inline void __init sgx_cgroup_register(void) { }
+static inline void sgx_cgroup_reclaim_pages_global(struct mm_struct *charge_mm) { }
+
#else /* CONFIG_CGROUP_MISC */
struct sgx_cgroup {
@@ -87,6 +89,7 @@ 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);
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 fa00ed5e884d..d00cb012838b 100644
--- a/arch/x86/kernel/cpu/sgx/main.c
+++ b/arch/x86/kernel/cpu/sgx/main.c
@@ -411,6 +411,13 @@ static bool sgx_should_reclaim_global(unsigned long watermark)
static void sgx_reclaim_pages_global(struct mm_struct *charge_mm)
{
+ /*
+ * Now all EPC pages are still tracked in the @sgx_global_lru.
+ * Still reclaim from it.
+ *
+ * When EPC pages are tracked in the actual per-cgroup LRUs,
+ * sgx_cgroup_reclaim_pages_global() will be called.
+ */
sgx_reclaim_pages(&sgx_global_lru, charge_mm);
}
--
2.43.0
