[Pal/Linux-SGX] EDMM Lazy free optimization

This optimization keeps track of free EPC pages and lazily frees them when the amount of EPC that is not freed exceeds a certain threshold that is set from the manifest file `sgx.edmm_lazyfree_th`. This optimization reduces enclave exists and at the same time doesn't hog EPC pages that aren't required anymore. Signed-off-by: Vijay Dhanraj <[email protected]>
gramineproject · Oct 4, 2021 · cd355a1 · cd355a1
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diff --git a/Documentation/manifest-syntax.rst b/Documentation/manifest-syntax.rst
@@ -460,6 +460,19 @@ the pages requested.
    New SGX driver IOCTL is experimental and is not yet available as part of official
    Intel SGX OOT driver release. This option is not yet ready for public usage.
 
+EDMM Lazy Free optimization (Experimental)
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+::
+
+    sgx.edmm_lazyfree_th = [NUM]
+    (Default: 0)
+
+This syntax specifies the **percentage** of total heap that can be freed in a lazy manner.
+Until this threshold is met, graphene doesn't release any dynamically allocated memory.
+This optimization helps reduce the expensive enclave entries/exits associated with dynamic
+freeing of EPC pages.
+
 Optional CPU features (AVX, AVX512, MPX, PKRU)
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 

diff --git a/Pal/src/host/Linux-SGX/Makefile b/Pal/src/host/Linux-SGX/Makefile
@@ -50,6 +50,7 @@ enclave-objs = \
 	db_sockets.o \
 	db_streams.o \
 	db_threading.o \
+	edmm_pages.o \
 	enclave_ecalls.o \
 	enclave_framework.o \
 	enclave_ocalls.o \

diff --git a/Pal/src/host/Linux-SGX/db_main.c b/Pal/src/host/Linux-SGX/db_main.c
@@ -610,6 +610,9 @@ noreturn void pal_linux_main(char* uptr_libpal_uri, size_t libpal_uri_len, char*
     /* Extract the mmap'd region to share addr and number of EPC pages requested with driver. */
     g_pal_sec.eaug_base = sec_info.eaug_base;
 
+    /* Extract enclave heap lazy free threshold */
+    g_pal_sec.edmm_lazyfree_th = sec_info.edmm_lazyfree_th;
+
     /* For {p,u,g}ids we can at least do some minimal checking. */
 
     /* ppid should be positive when interpreted as signed. It's 0 if we don't