On Sat, 9 Apr 2011, Sasha Levin wrote:
Attempt to use mmap first for working with a disk image, if the attempt is failed (for example, large image on a 32bit system) fallback to using read/write.
Performance (kB/s) test using bonnie++ showed the following improvement:
Sequential write: 14%
Sequential rewrite: 15%
Sequential read: 7%
Random seek latency: 82%
Can you also please share the before and after raw data?
-struct disk_image *disk_image__new(int fd, uint64_t size, struct disk_image_operations *ops)
+static int raw_image__read_sector_mmap(struct disk_image *self, uint64_t sector, void *dst, uint32_t dst_len)
{
- struct disk_image *self;
+ uint64_t offset = sector << SECTOR_SHIFT;
- self = malloc(sizeof *self);
- if (!self)
- return NULL;
+ if (offset + dst_len > self->size)
+ return -1;
- self->fd = fd;
- self->size = size;
- self->ops = ops;
+ memmove(dst, self->mapping + offset, dst_len);
Why do you want to use memmove() here? The areas cannot overlap.
Pekka
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