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Date: Mon, 2 Jul 2012 16:15:49 -0500
From: Seth Jennings <sjenning@...ux.vnet.ibm.com>
To: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: Seth Jennings <sjenning@...ux.vnet.ibm.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Dan Magenheimer <dan.magenheimer@...cle.com>,
Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
Nitin Gupta <ngupta@...are.org>,
Minchan Kim <minchan@...nel.org>,
Robert Jennings <rcj@...ux.vnet.ibm.com>, linux-mm@...ck.org,
devel@...verdev.osuosl.org, linux-kernel@...r.kernel.org
Subject: [PATCH 1/4] zsmalloc: remove x86 dependency
This patch replaces the page table assisted object mapping
method, which has x86 dependencies, with a arch-independent
method that does a simple copy into a temporary per-cpu
buffer.
While a copy seems like it would be worse than mapping the pages,
tests demonstrate the copying is always faster and, in the case of
running inside a KVM guest, roughly 4x faster.
Signed-off-by: Seth Jennings <sjenning@...ux.vnet.ibm.com>
---
drivers/staging/zsmalloc/Kconfig | 4 --
drivers/staging/zsmalloc/zsmalloc-main.c | 99 +++++++++++++++++++++---------
drivers/staging/zsmalloc/zsmalloc_int.h | 5 +-
3 files changed, 72 insertions(+), 36 deletions(-)
diff --git a/drivers/staging/zsmalloc/Kconfig b/drivers/staging/zsmalloc/Kconfig
index a5ab720..9084565 100644
--- a/drivers/staging/zsmalloc/Kconfig
+++ b/drivers/staging/zsmalloc/Kconfig
@@ -1,9 +1,5 @@
config ZSMALLOC
tristate "Memory allocator for compressed pages"
- # X86 dependency is because of the use of __flush_tlb_one and set_pte
- # in zsmalloc-main.c.
- # TODO: convert these to portable functions
- depends on X86
default n
help
zsmalloc is a slab-based memory allocator designed to store
diff --git a/drivers/staging/zsmalloc/zsmalloc-main.c b/drivers/staging/zsmalloc/zsmalloc-main.c
index 10b0d60..a7a6f22 100644
--- a/drivers/staging/zsmalloc/zsmalloc-main.c
+++ b/drivers/staging/zsmalloc/zsmalloc-main.c
@@ -470,6 +470,57 @@ static struct page *find_get_zspage(struct size_class *class)
return page;
}
+static void zs_copy_map_object(char *buf, struct page *firstpage,
+ int off, int size)
+{
+ struct page *pages[2];
+ int sizes[2];
+ void *addr;
+
+ pages[0] = firstpage;
+ pages[1] = get_next_page(firstpage);
+ BUG_ON(!pages[1]);
+
+ sizes[0] = PAGE_SIZE - off;
+ sizes[1] = size - sizes[0];
+
+ /* disable page faults to match kmap_atomic() return conditions */
+ pagefault_disable();
+
+ /* copy object to per-cpu buffer */
+ addr = kmap_atomic(pages[0]);
+ memcpy(buf, addr + off, sizes[0]);
+ kunmap_atomic(addr);
+ addr = kmap_atomic(pages[1]);
+ memcpy(buf + sizes[0], addr, sizes[1]);
+ kunmap_atomic(addr);
+}
+
+static void zs_copy_unmap_object(char *buf, struct page *firstpage,
+ int off, int size)
+{
+ struct page *pages[2];
+ int sizes[2];
+ void *addr;
+
+ pages[0] = firstpage;
+ pages[1] = get_next_page(firstpage);
+ BUG_ON(!pages[1]);
+
+ sizes[0] = PAGE_SIZE - off;
+ sizes[1] = size - sizes[0];
+
+ /* copy per-cpu buffer to object */
+ addr = kmap_atomic(pages[0]);
+ memcpy(addr + off, buf, sizes[0]);
+ kunmap_atomic(addr);
+ addr = kmap_atomic(pages[1]);
+ memcpy(addr, buf + sizes[0], sizes[1]);
+ kunmap_atomic(addr);
+
+ /* enable page faults to match kunmap_atomic() return conditions */
+ pagefault_enable();
+}
static int zs_cpu_notifier(struct notifier_block *nb, unsigned long action,
void *pcpu)
@@ -480,18 +531,23 @@ static int zs_cpu_notifier(struct notifier_block *nb, unsigned long action,
switch (action) {
case CPU_UP_PREPARE:
area = &per_cpu(zs_map_area, cpu);
- if (area->vm)
- break;
- area->vm = alloc_vm_area(2 * PAGE_SIZE, area->vm_ptes);
- if (!area->vm)
- return notifier_from_errno(-ENOMEM);
+ /*
+ * Make sure we don't leak memory if a cpu UP notification
+ * and zs_init() race and both call zs_cpu_up() on the same cpu
+ */
+ if (area->vm_buf)
+ return 0;
+ area->vm_buf = (char *)__get_free_page(GFP_KERNEL);
+ if (!area->vm_buf)
+ return -ENOMEM;
+ return 0;
break;
case CPU_DEAD:
case CPU_UP_CANCELED:
area = &per_cpu(zs_map_area, cpu);
- if (area->vm)
- free_vm_area(area->vm);
- area->vm = NULL;
+ if (area->vm_buf)
+ free_page((unsigned long)area->vm_buf);
+ area->vm_buf = NULL;
break;
}
@@ -714,22 +770,11 @@ void *zs_map_object(struct zs_pool *pool, unsigned long handle)
if (off + class->size <= PAGE_SIZE) {
/* this object is contained entirely within a page */
area->vm_addr = kmap_atomic(page);
- } else {
- /* this object spans two pages */
- struct page *nextp;
-
- nextp = get_next_page(page);
- BUG_ON(!nextp);
-
-
- set_pte(area->vm_ptes[0], mk_pte(page, PAGE_KERNEL));
- set_pte(area->vm_ptes[1], mk_pte(nextp, PAGE_KERNEL));
-
- /* We pre-allocated VM area so mapping can never fail */
- area->vm_addr = area->vm->addr;
+ return area->vm_addr + off;
}
- return area->vm_addr + off;
+ zs_copy_map_object(area->vm_buf, page, off, class->size);
+ return area->vm_buf;
}
EXPORT_SYMBOL_GPL(zs_map_object);
@@ -751,14 +796,10 @@ void zs_unmap_object(struct zs_pool *pool, unsigned long handle)
off = obj_idx_to_offset(page, obj_idx, class->size);
area = &__get_cpu_var(zs_map_area);
- if (off + class->size <= PAGE_SIZE) {
+ if (off + class->size <= PAGE_SIZE)
kunmap_atomic(area->vm_addr);
- } else {
- set_pte(area->vm_ptes[0], __pte(0));
- set_pte(area->vm_ptes[1], __pte(0));
- __flush_tlb_one((unsigned long)area->vm_addr);
- __flush_tlb_one((unsigned long)area->vm_addr + PAGE_SIZE);
- }
+ else
+ zs_copy_unmap_object(area->vm_buf, page, off, class->size);
put_cpu_var(zs_map_area);
}
EXPORT_SYMBOL_GPL(zs_unmap_object);
diff --git a/drivers/staging/zsmalloc/zsmalloc_int.h b/drivers/staging/zsmalloc/zsmalloc_int.h
index 6fd32a9..f760dae 100644
--- a/drivers/staging/zsmalloc/zsmalloc_int.h
+++ b/drivers/staging/zsmalloc/zsmalloc_int.h
@@ -110,9 +110,8 @@ enum fullness_group {
static const int fullness_threshold_frac = 4;
struct mapping_area {
- struct vm_struct *vm;
- pte_t *vm_ptes[2];
- char *vm_addr;
+ char *vm_buf; /* copy buffer for objects that span pages */
+ char *vm_addr; /* address of kmap_atomic()'ed pages */
};
struct size_class {
--
1.7.9.5
--
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