From 5d4d9902fa2772575b336056595f2e4a5b213dc1 Mon Sep 17 00:00:00 2001 From: Sasha Levin Date: Sat, 9 Apr 2011 20:07:59 +0300 Subject: [PATCH] kvm tools: Use mmap by default for disk images Use mmap() for disk images and fallback to read()/write() if it fails (for example, with large images on 32 bit systems). Performance (kB/s) test using bonnie++ shows 19% improvement in block writes, 7% improvement in block rewrites, and 6% improvement in block reads. Guest was started with the following command: ./kvm run --mem=256 --image=./work/vms/gentoo.img --kernel=/boot/bzImage-git and bonnie++ with: bonnie++ -u 0 Before: ------ Version 1.96 ------Sequential Output----- --Sequential Input- -Random- Concurrency 1 -Per Chr- --Block-- -Rewrite- -Per Chr- --Block-- --Seeks-- Machine Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP /sec %CP tux 480M 673 100 308017 61 288156 49 3286 99 892186 76 +++++ +++ Latency 12998us 50992us 35993us 3000us 1999us 201ms Version 1.96 ------Sequential Create------ --------Random Create-------- tux -Create-- --Read--- -Delete-- -Create-- --Read--- -Delete-- files /sec %CP /sec %CP /sec %CP /sec %CP /sec %CP /sec %CP 16 +++++ +++ +++++ +++ +++++ +++ +++++ +++ +++++ +++ +++++ +++ Latency 3000us 1000us 1000us 1000us 1998us 1000us After: ------ Version 1.96 ------Sequential Output------ --Sequential Input- --Random- Concurrency 1 -Per Chr- --Block-- -Rewrite- -Per Chr- --Block-- --Seeks-- Machine Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP /sec %CP tux 480M 674 99 366588 42 309514 44 3539 99 954554 76 +++++ +++ Latency 17997us 15997us 37993us 4999us 1998us 145ms Version 1.96 ------Sequential Create------ --------Random Create-------- tux -Create-- --Read--- -Delete-- -Create-- --Read--- -Delete-- files /sec %CP /sec %CP /sec %CP /sec %CP /sec %CP /sec %CP 16 +++++ +++ +++++ +++ +++++ +++ +++++ +++ +++++ +++ +++++ +++ Latency 1000us 1000us 2000us 1999us 1000us 1000us [ penberg@kernel.org: drop MAP_NORESERVE, it's no-op for MAP_SHARED ] Signed-off-by: Sasha Levin Signed-off-by: Pekka Enberg --- disk-image.c | 54 ++++++++++++++++++++++++++++++++-------- include/kvm/disk-image.h | 2 +- 2 files changed, 45 insertions(+), 11 deletions(-) diff --git a/disk-image.c b/disk-image.c index 9deaf45..d94057a 100644 --- a/disk-image.c +++ b/disk-image.c @@ -13,21 +13,31 @@ #include #include -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; + memcpy(dst, self->priv + 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; + + memcpy(self->priv + 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->priv = mmap(NULL, size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0); + self->ops = (self->priv == 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->priv != MAP_FAILED) + munmap(self->priv, self->size); + if (close(self->fd) < 0) warning("close() failed"); diff --git a/include/kvm/disk-image.h b/include/kvm/disk-image.h index df0a15d..8b78657 100644 --- a/include/kvm/disk-image.h +++ b/include/kvm/disk-image.h @@ -22,7 +22,7 @@ struct disk_image { }; 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)