xen: cleancache shim to Xen Transcendent Memory
This patch provides a shim between the kernel-internal cleancache
API (see Documentation/mm/cleancache.txt) and the Xen Transcendent
Memory ABI (see http://oss.oracle.com/projects/tmem).
Xen tmem provides "hypervisor RAM" as an ephemeral page-oriented
pseudo-RAM store for cleancache pages, shared cleancache pages,
and frontswap pages. Tmem provides enterprise-quality concurrency,
full save/restore and live migration support, compression
and deduplication.
A presentation showing up to 8% faster performance and up to 52%
reduction in sectors read on a kernel compile workload, despite
aggressive in-kernel page reclamation ("self-ballooning") can be
found at:
http://oss.oracle.com/projects/tmem/dist/documentation/presentations/TranscendentMemoryXenSummit2010.pdf
Signed-off-by: Dan Magenheimer <dan.magenheimer@oracle.com>
Reviewed-by: Jeremy Fitzhardinge <jeremy@goop.org>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Matthew Wilcox <matthew@wil.cx>
Cc: Nick Piggin <npiggin@kernel.dk>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: Rik Van Riel <riel@redhat.com>
Cc: Jan Beulich <JBeulich@novell.com>
Cc: Chris Mason <chris.mason@oracle.com>
Cc: Andreas Dilger <adilger@sun.com>
Cc: Ted Ts'o <tytso@mit.edu>
Cc: Mark Fasheh <mfasheh@suse.com>
Cc: Joel Becker <joel.becker@oracle.com>
Cc: Nitin Gupta <ngupta@vflare.org>
diff --git a/drivers/xen/tmem.c b/drivers/xen/tmem.c
new file mode 100644
index 0000000..816a449
--- /dev/null
+++ b/drivers/xen/tmem.c
@@ -0,0 +1,264 @@
+/*
+ * Xen implementation for transcendent memory (tmem)
+ *
+ * Copyright (C) 2009-2010 Oracle Corp. All rights reserved.
+ * Author: Dan Magenheimer
+ */
+
+#include <linux/kernel.h>
+#include <linux/types.h>
+#include <linux/init.h>
+#include <linux/pagemap.h>
+#include <linux/cleancache.h>
+
+#include <xen/xen.h>
+#include <xen/interface/xen.h>
+#include <asm/xen/hypercall.h>
+#include <asm/xen/page.h>
+#include <asm/xen/hypervisor.h>
+
+#define TMEM_CONTROL 0
+#define TMEM_NEW_POOL 1
+#define TMEM_DESTROY_POOL 2
+#define TMEM_NEW_PAGE 3
+#define TMEM_PUT_PAGE 4
+#define TMEM_GET_PAGE 5
+#define TMEM_FLUSH_PAGE 6
+#define TMEM_FLUSH_OBJECT 7
+#define TMEM_READ 8
+#define TMEM_WRITE 9
+#define TMEM_XCHG 10
+
+/* Bits for HYPERVISOR_tmem_op(TMEM_NEW_POOL) */
+#define TMEM_POOL_PERSIST 1
+#define TMEM_POOL_SHARED 2
+#define TMEM_POOL_PAGESIZE_SHIFT 4
+#define TMEM_VERSION_SHIFT 24
+
+
+struct tmem_pool_uuid {
+ u64 uuid_lo;
+ u64 uuid_hi;
+};
+
+struct tmem_oid {
+ u64 oid[3];
+};
+
+#define TMEM_POOL_PRIVATE_UUID { 0, 0 }
+
+/* flags for tmem_ops.new_pool */
+#define TMEM_POOL_PERSIST 1
+#define TMEM_POOL_SHARED 2
+
+/* xen tmem foundation ops/hypercalls */
+
+static inline int xen_tmem_op(u32 tmem_cmd, u32 tmem_pool, struct tmem_oid oid,
+ u32 index, unsigned long gmfn, u32 tmem_offset, u32 pfn_offset, u32 len)
+{
+ struct tmem_op op;
+ int rc = 0;
+
+ op.cmd = tmem_cmd;
+ op.pool_id = tmem_pool;
+ op.u.gen.oid[0] = oid.oid[0];
+ op.u.gen.oid[1] = oid.oid[1];
+ op.u.gen.oid[2] = oid.oid[2];
+ op.u.gen.index = index;
+ op.u.gen.tmem_offset = tmem_offset;
+ op.u.gen.pfn_offset = pfn_offset;
+ op.u.gen.len = len;
+ set_xen_guest_handle(op.u.gen.gmfn, (void *)gmfn);
+ rc = HYPERVISOR_tmem_op(&op);
+ return rc;
+}
+
+static int xen_tmem_new_pool(struct tmem_pool_uuid uuid,
+ u32 flags, unsigned long pagesize)
+{
+ struct tmem_op op;
+ int rc = 0, pageshift;
+
+ for (pageshift = 0; pagesize != 1; pageshift++)
+ pagesize >>= 1;
+ flags |= (pageshift - 12) << TMEM_POOL_PAGESIZE_SHIFT;
+ flags |= TMEM_SPEC_VERSION << TMEM_VERSION_SHIFT;
+ op.cmd = TMEM_NEW_POOL;
+ op.u.new.uuid[0] = uuid.uuid_lo;
+ op.u.new.uuid[1] = uuid.uuid_hi;
+ op.u.new.flags = flags;
+ rc = HYPERVISOR_tmem_op(&op);
+ return rc;
+}
+
+/* xen generic tmem ops */
+
+static int xen_tmem_put_page(u32 pool_id, struct tmem_oid oid,
+ u32 index, unsigned long pfn)
+{
+ unsigned long gmfn = xen_pv_domain() ? pfn_to_mfn(pfn) : pfn;
+
+ return xen_tmem_op(TMEM_PUT_PAGE, pool_id, oid, index,
+ gmfn, 0, 0, 0);
+}
+
+static int xen_tmem_get_page(u32 pool_id, struct tmem_oid oid,
+ u32 index, unsigned long pfn)
+{
+ unsigned long gmfn = xen_pv_domain() ? pfn_to_mfn(pfn) : pfn;
+
+ return xen_tmem_op(TMEM_GET_PAGE, pool_id, oid, index,
+ gmfn, 0, 0, 0);
+}
+
+static int xen_tmem_flush_page(u32 pool_id, struct tmem_oid oid, u32 index)
+{
+ return xen_tmem_op(TMEM_FLUSH_PAGE, pool_id, oid, index,
+ 0, 0, 0, 0);
+}
+
+static int xen_tmem_flush_object(u32 pool_id, struct tmem_oid oid)
+{
+ return xen_tmem_op(TMEM_FLUSH_OBJECT, pool_id, oid, 0, 0, 0, 0, 0);
+}
+
+static int xen_tmem_destroy_pool(u32 pool_id)
+{
+ struct tmem_oid oid = { { 0 } };
+
+ return xen_tmem_op(TMEM_DESTROY_POOL, pool_id, oid, 0, 0, 0, 0, 0);
+}
+
+int tmem_enabled;
+
+static int __init enable_tmem(char *s)
+{
+ tmem_enabled = 1;
+ return 1;
+}
+
+__setup("tmem", enable_tmem);
+
+/* cleancache ops */
+
+static void tmem_cleancache_put_page(int pool, struct cleancache_filekey key,
+ pgoff_t index, struct page *page)
+{
+ u32 ind = (u32) index;
+ struct tmem_oid oid = *(struct tmem_oid *)&key;
+ unsigned long pfn = page_to_pfn(page);
+
+ if (pool < 0)
+ return;
+ if (ind != index)
+ return;
+ mb(); /* ensure page is quiescent; tmem may address it with an alias */
+ (void)xen_tmem_put_page((u32)pool, oid, ind, pfn);
+}
+
+static int tmem_cleancache_get_page(int pool, struct cleancache_filekey key,
+ pgoff_t index, struct page *page)
+{
+ u32 ind = (u32) index;
+ struct tmem_oid oid = *(struct tmem_oid *)&key;
+ unsigned long pfn = page_to_pfn(page);
+ int ret;
+
+ /* translate return values to linux semantics */
+ if (pool < 0)
+ return -1;
+ if (ind != index)
+ return -1;
+ ret = xen_tmem_get_page((u32)pool, oid, ind, pfn);
+ if (ret == 1)
+ return 0;
+ else
+ return -1;
+}
+
+static void tmem_cleancache_flush_page(int pool, struct cleancache_filekey key,
+ pgoff_t index)
+{
+ u32 ind = (u32) index;
+ struct tmem_oid oid = *(struct tmem_oid *)&key;
+
+ if (pool < 0)
+ return;
+ if (ind != index)
+ return;
+ (void)xen_tmem_flush_page((u32)pool, oid, ind);
+}
+
+static void tmem_cleancache_flush_inode(int pool, struct cleancache_filekey key)
+{
+ struct tmem_oid oid = *(struct tmem_oid *)&key;
+
+ if (pool < 0)
+ return;
+ (void)xen_tmem_flush_object((u32)pool, oid);
+}
+
+static void tmem_cleancache_flush_fs(int pool)
+{
+ if (pool < 0)
+ return;
+ (void)xen_tmem_destroy_pool((u32)pool);
+}
+
+static int tmem_cleancache_init_fs(size_t pagesize)
+{
+ struct tmem_pool_uuid uuid_private = TMEM_POOL_PRIVATE_UUID;
+
+ return xen_tmem_new_pool(uuid_private, 0, pagesize);
+}
+
+static int tmem_cleancache_init_shared_fs(char *uuid, size_t pagesize)
+{
+ struct tmem_pool_uuid shared_uuid;
+
+ shared_uuid.uuid_lo = *(u64 *)uuid;
+ shared_uuid.uuid_hi = *(u64 *)(&uuid[8]);
+ return xen_tmem_new_pool(shared_uuid, TMEM_POOL_SHARED, pagesize);
+}
+
+static int use_cleancache = 1;
+
+static int __init no_cleancache(char *s)
+{
+ use_cleancache = 0;
+ return 1;
+}
+
+__setup("nocleancache", no_cleancache);
+
+static struct cleancache_ops tmem_cleancache_ops = {
+ .put_page = tmem_cleancache_put_page,
+ .get_page = tmem_cleancache_get_page,
+ .flush_page = tmem_cleancache_flush_page,
+ .flush_inode = tmem_cleancache_flush_inode,
+ .flush_fs = tmem_cleancache_flush_fs,
+ .init_shared_fs = tmem_cleancache_init_shared_fs,
+ .init_fs = tmem_cleancache_init_fs
+};
+
+static int __init xen_tmem_init(void)
+{
+ struct cleancache_ops old_ops;
+
+ if (!xen_domain())
+ return 0;
+#ifdef CONFIG_CLEANCACHE
+ BUG_ON(sizeof(struct cleancache_filekey) != sizeof(struct tmem_oid));
+ if (tmem_enabled && use_cleancache) {
+ char *s = "";
+ old_ops = cleancache_register_ops(&tmem_cleancache_ops);
+ if (old_ops.init_fs != NULL)
+ s = " (WARNING: cleancache_ops overridden)";
+ printk(KERN_INFO "cleancache enabled, RAM provided by "
+ "Xen Transcendent Memory%s\n", s);
+ }
+#endif
+ return 0;
+}
+
+module_init(xen_tmem_init)