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Date: Sat, 29 Mar 2008 18:46:05 +0100
From: Borislav Petkov <petkovbb@...glemail.com>
To: <bzolnier@...il.com>
Cc: linux-kernel@...r.kernel.org, linux-ide@...r.kernel.org,
Borislav Petkov <petkovbb@...il.com>
Subject: [PATCH 1/5] ide-tape: improve buffer allocation strategy
Instead of allocating pages for the buffer one by one, take advantage of the
buddy alloc system and request them 2^order at a time. This increases the chance
for bigger buffer parts to be contigious and reduces loop iteration count. While
at it, rename function __idetape_kmalloc_stage() to ide_tape_kmalloc_buffer().
Signed-off-by: Borislav Petkov <petkovbb@...il.com>
---
drivers/ide/ide-tape.c | 58 +++++++++++++++++++++++++++++------------------
1 files changed, 36 insertions(+), 22 deletions(-)
diff --git a/drivers/ide/ide-tape.c b/drivers/ide/ide-tape.c
index 6752d47..b5ec669 100644
--- a/drivers/ide/ide-tape.c
+++ b/drivers/ide/ide-tape.c
@@ -1290,20 +1290,20 @@ out:
}
/*
- * The function below uses __get_free_page to allocate a pipeline stage, along
- * with all the necessary small buffers which together make a buffer of size
+ * The function below uses __get_free_pages to allocate a data buffer of size
* tape->stage_size (or a bit more). We attempt to combine sequential pages as
* much as possible.
*
- * It returns a pointer to the new allocated stage, or NULL if we can't (or
- * don't want to) allocate a stage.
+ * It returns a pointer to the newly allocated buffer, or NULL in case of
+ * failure.
*/
-static idetape_stage_t *__idetape_kmalloc_stage(idetape_tape_t *tape, int full,
+static idetape_stage_t *ide_tape_kmalloc_buffer(idetape_tape_t *tape, int full,
int clear)
{
idetape_stage_t *stage;
struct idetape_bh *prev_bh, *bh;
int pages = tape->pages_per_stage;
+ unsigned int order, b_allocd;
char *b_data = NULL;
stage = kmalloc(sizeof(idetape_stage_t), GFP_KERNEL);
@@ -1315,32 +1315,43 @@ static idetape_stage_t *__idetape_kmalloc_stage(idetape_tape_t *tape, int full,
bh = stage->bh;
if (bh == NULL)
goto abort;
- bh->b_reqnext = NULL;
- bh->b_data = (char *) __get_free_page(GFP_KERNEL);
+
+ order = fls(pages) - 1;
+ bh->b_data = (char *) __get_free_pages(GFP_KERNEL, order);
if (!bh->b_data)
goto abort;
+ b_allocd = (1 << order) * PAGE_SIZE;
+ pages &= (order-1);
+
if (clear)
- memset(bh->b_data, 0, PAGE_SIZE);
- bh->b_size = PAGE_SIZE;
+ memset(bh->b_data, 0, b_allocd);
+ bh->b_reqnext = NULL;
+ bh->b_size = b_allocd;
atomic_set(&bh->b_count, full ? bh->b_size : 0);
- while (--pages) {
- b_data = (char *) __get_free_page(GFP_KERNEL);
+ while (pages) {
+ order = fls(pages) - 1;
+ b_data = (char *) __get_free_pages(GFP_KERNEL, order);
if (!b_data)
goto abort;
+ b_allocd = (1 << order) * PAGE_SIZE;
+
if (clear)
- memset(b_data, 0, PAGE_SIZE);
- if (bh->b_data == b_data + PAGE_SIZE) {
- bh->b_size += PAGE_SIZE;
- bh->b_data -= PAGE_SIZE;
+ memset(b_data, 0, b_allocd);
+
+ /* newly allocated page frames below buffer header or ...*/
+ if (bh->b_data == b_data + b_allocd) {
+ bh->b_size += b_allocd;
+ bh->b_data -= b_allocd;
if (full)
- atomic_add(PAGE_SIZE, &bh->b_count);
+ atomic_add(b_allocd, &bh->b_count);
continue;
}
+ /* they are above the header */
if (b_data == bh->b_data + bh->b_size) {
- bh->b_size += PAGE_SIZE;
+ bh->b_size += b_allocd;
if (full)
- atomic_add(PAGE_SIZE, &bh->b_count);
+ atomic_add(b_allocd, &bh->b_count);
continue;
}
prev_bh = bh;
@@ -1351,10 +1362,13 @@ static idetape_stage_t *__idetape_kmalloc_stage(idetape_tape_t *tape, int full,
}
bh->b_reqnext = NULL;
bh->b_data = b_data;
- bh->b_size = PAGE_SIZE;
+ bh->b_size = b_allocd;
atomic_set(&bh->b_count, full ? bh->b_size : 0);
prev_bh->b_reqnext = bh;
+
+ pages &= (order-1);
}
+
bh->b_size -= tape->excess_bh_size;
if (full)
atomic_sub(tape->excess_bh_size, &bh->b_count);
@@ -1837,7 +1851,7 @@ static int idetape_init_read(ide_drive_t *drive)
" 0 now\n");
tape->merge_stage_size = 0;
}
- tape->merge_stage = __idetape_kmalloc_stage(tape, 0, 0);
+ tape->merge_stage = ide_tape_kmalloc_buffer(tape, 0, 0);
if (!tape->merge_stage)
return -ENOMEM;
tape->chrdev_dir = IDETAPE_DIR_READ;
@@ -2115,7 +2129,7 @@ static ssize_t idetape_chrdev_write(struct file *file, const char __user *buf,
"should be 0 now\n");
tape->merge_stage_size = 0;
}
- tape->merge_stage = __idetape_kmalloc_stage(tape, 0, 0);
+ tape->merge_stage = ide_tape_kmalloc_buffer(tape, 0, 0);
if (!tape->merge_stage)
return -ENOMEM;
tape->chrdev_dir = IDETAPE_DIR_WRITE;
@@ -2495,7 +2509,7 @@ static void idetape_write_release(ide_drive_t *drive, unsigned int minor)
idetape_tape_t *tape = drive->driver_data;
idetape_empty_write_pipeline(drive);
- tape->merge_stage = __idetape_kmalloc_stage(tape, 1, 0);
+ tape->merge_stage = ide_tape_kmalloc_buffer(tape, 1, 0);
if (tape->merge_stage != NULL) {
idetape_pad_zeros(drive, tape->blk_size *
(tape->user_bs_factor - 1));
--
1.5.4.1
--
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