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% Signed-off-by: Sasha Levin <[email protected]> --- tools/kvm/disk-image.c | 54 +++++++++++++++++++++++++++++------ tools/kvm/include/kvm/disk-image.h | 3 +- 2 files changed, 46 insertions(+), 11 deletions(-) diff --git a/tools/kvm/disk-image.c b/tools/kvm/disk-image.c index 9deaf45..ae2fa2a 100644 --- a/tools/kvm/disk-image.c +++ b/tools/kvm/disk-image.c @@ -13,21 +13,31 @@ #include <unistd.h> #include <fcntl.h> -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); - return self; + return 0; +} + +static int raw_image__write_sector_mmap(struct disk_image *self, uint64_t sector, void *src, uint32_t src_len) +{ + uint64_t offset = sector << SECTOR_SHIFT; + + if (offset + src_len > self->size) + return -1; + + memmove(self->mapping + offset, src, src_len); + + return 0; } + static int raw_image__read_sector(struct disk_image *self, uint64_t sector, void *dst, uint32_t dst_len) { uint64_t offset = sector << SECTOR_SHIFT; @@ -59,6 +69,27 @@ static struct disk_image_operations raw_image_ops = { .write_sector = raw_image__write_sector, }; +static struct disk_image_operations raw_image_mmap_ops = { + .read_sector = raw_image__read_sector_mmap, + .write_sector = raw_image__write_sector_mmap, +}; + +struct disk_image *disk_image__new(int fd, uint64_t size) +{ + struct disk_image *self; + + self = malloc(sizeof *self); + if (!self) + return NULL; + + self->fd = fd; + self->size = size; + self->mapping = mmap(NULL, size, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_NORESERVE, fd, 0); + self->ops = (self->mapping == MAP_FAILED) ? &raw_image_ops : &raw_image_mmap_ops; + + return self; +} + static struct disk_image *raw_image__probe(int fd) { struct stat st; @@ -66,7 +97,7 @@ static struct disk_image *raw_image__probe(int fd) if (fstat(fd, &st) < 0) return NULL; - return disk_image__new(fd, st.st_size, &raw_image_ops); + return disk_image__new(fd, st.st_size); } struct disk_image *disk_image__open(const char *filename) @@ -97,6 +128,9 @@ void disk_image__close(struct disk_image *self) if (self->ops->close) self->ops->close(self); + if (self->mapping != MAP_FAILED) + munmap(self->mapping, self->size); + if (close(self->fd) < 0) warning("close() failed"); diff --git a/tools/kvm/include/kvm/disk-image.h b/tools/kvm/include/kvm/disk-image.h index df0a15d..001a8d5 100644 --- a/tools/kvm/include/kvm/disk-image.h +++ b/tools/kvm/include/kvm/disk-image.h @@ -18,11 +18,12 @@ struct disk_image { int fd; uint64_t size; struct disk_image_operations *ops; + void *mapping; void *priv; }; struct disk_image *disk_image__open(const char *filename); -struct disk_image *disk_image__new(int fd, uint64_t size, struct disk_image_operations *ops); +struct disk_image *disk_image__new(int fd, uint64_t size); void disk_image__close(struct disk_image *self); static inline int disk_image__read_sector(struct disk_image *self, uint64_t sector, void *dst, uint32_t dst_len) -- 1.7.5.rc1 -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
