From bcfeacab45e6d419c6bafc0e57ea4b1125e23231 Mon Sep 17 00:00:00 2001 From: Igor Mammedov Date: Tue, 16 Jun 2015 18:33:35 +0200 Subject: vhost: use binary search instead of linear in find_region() For default region layouts performance stays the same as linear search i.e. it takes around 210ns average for translate_desc() that inlines find_region(). But it scales better with larger amount of regions, 235ns BS vs 300ns LS with 55 memory regions and it will be about the same values when allowed number of slots is increased to 509 like it has been done in kvm. Signed-off-by: Igor Mammedov Signed-off-by: Michael S. Tsirkin --- drivers/vhost/vhost.c | 38 ++++++++++++++++++++++++++++---------- 1 file changed, 28 insertions(+), 10 deletions(-) (limited to 'drivers/vhost') diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c index 9e8e004bb1c3..71bb46813031 100644 --- a/drivers/vhost/vhost.c +++ b/drivers/vhost/vhost.c @@ -25,6 +25,7 @@ #include #include #include +#include #include "vhost.h" @@ -663,6 +664,16 @@ int vhost_vq_access_ok(struct vhost_virtqueue *vq) } EXPORT_SYMBOL_GPL(vhost_vq_access_ok); +static int vhost_memory_reg_sort_cmp(const void *p1, const void *p2) +{ + const struct vhost_memory_region *r1 = p1, *r2 = p2; + if (r1->guest_phys_addr < r2->guest_phys_addr) + return 1; + if (r1->guest_phys_addr > r2->guest_phys_addr) + return -1; + return 0; +} + static long vhost_set_memory(struct vhost_dev *d, struct vhost_memory __user *m) { struct vhost_memory mem, *newmem, *oldmem; @@ -682,9 +693,11 @@ static long vhost_set_memory(struct vhost_dev *d, struct vhost_memory __user *m) memcpy(newmem, &mem, size); if (copy_from_user(newmem->regions, m->regions, mem.nregions * sizeof *m->regions)) { - kfree(newmem); + kvfree(newmem); return -EFAULT; } + sort(newmem->regions, newmem->nregions, sizeof(*newmem->regions), + vhost_memory_reg_sort_cmp, NULL); if (!memory_access_ok(d, newmem, 0)) { kfree(newmem); @@ -992,17 +1005,22 @@ EXPORT_SYMBOL_GPL(vhost_dev_ioctl); static const struct vhost_memory_region *find_region(struct vhost_memory *mem, __u64 addr, __u32 len) { - struct vhost_memory_region *reg; - int i; + const struct vhost_memory_region *reg; + int start = 0, end = mem->nregions; - /* linear search is not brilliant, but we really have on the order of 6 - * regions in practice */ - for (i = 0; i < mem->nregions; ++i) { - reg = mem->regions + i; - if (reg->guest_phys_addr <= addr && - reg->guest_phys_addr + reg->memory_size - 1 >= addr) - return reg; + while (start < end) { + int slot = start + (end - start) / 2; + reg = mem->regions + slot; + if (addr >= reg->guest_phys_addr) + end = slot; + else + start = slot + 1; } + + reg = mem->regions + start; + if (addr >= reg->guest_phys_addr && + reg->guest_phys_addr + reg->memory_size > addr) + return reg; return NULL; } -- cgit v1.2.3 From 4de7255f7d2be5e51664c6ac6011ffd6e5463571 Mon Sep 17 00:00:00 2001 From: Igor Mammedov Date: Wed, 1 Jul 2015 11:07:09 +0200 Subject: vhost: extend memory regions allocation to vmalloc with large number of memory regions we could end up with high order allocations and kmalloc could fail if host is under memory pressure. Considering that memory regions array is used on hot path try harder to allocate using kmalloc and if it fails resort to vmalloc. It's still better than just failing vhost_set_memory() and causing guest crash due to it when a new memory hotplugged to guest. I'll still look at QEMU side solution to reduce amount of memory regions it feeds to vhost to make things even better, but it doesn't hurt for kernel to behave smarter and don't crash older QEMU's which could use large amount of memory regions. Signed-off-by: Igor Mammedov Signed-off-by: Michael S. Tsirkin --- drivers/vhost/vhost.c | 21 +++++++++++++++++---- 1 file changed, 17 insertions(+), 4 deletions(-) (limited to 'drivers/vhost') diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c index 71bb46813031..a4ac369f6adb 100644 --- a/drivers/vhost/vhost.c +++ b/drivers/vhost/vhost.c @@ -22,6 +22,7 @@ #include #include #include +#include #include #include #include @@ -544,7 +545,7 @@ void vhost_dev_cleanup(struct vhost_dev *dev, bool locked) fput(dev->log_file); dev->log_file = NULL; /* No one will access memory at this point */ - kfree(dev->memory); + kvfree(dev->memory); dev->memory = NULL; WARN_ON(!list_empty(&dev->work_list)); if (dev->worker) { @@ -674,6 +675,18 @@ static int vhost_memory_reg_sort_cmp(const void *p1, const void *p2) return 0; } +static void *vhost_kvzalloc(unsigned long size) +{ + void *n = kzalloc(size, GFP_KERNEL | __GFP_NOWARN | __GFP_REPEAT); + + if (!n) { + n = vzalloc(size); + if (!n) + return ERR_PTR(-ENOMEM); + } + return n; +} + static long vhost_set_memory(struct vhost_dev *d, struct vhost_memory __user *m) { struct vhost_memory mem, *newmem, *oldmem; @@ -686,7 +699,7 @@ static long vhost_set_memory(struct vhost_dev *d, struct vhost_memory __user *m) return -EOPNOTSUPP; if (mem.nregions > VHOST_MEMORY_MAX_NREGIONS) return -E2BIG; - newmem = kmalloc(size + mem.nregions * sizeof *m->regions, GFP_KERNEL); + newmem = vhost_kvzalloc(size + mem.nregions * sizeof(*m->regions)); if (!newmem) return -ENOMEM; @@ -700,7 +713,7 @@ static long vhost_set_memory(struct vhost_dev *d, struct vhost_memory __user *m) vhost_memory_reg_sort_cmp, NULL); if (!memory_access_ok(d, newmem, 0)) { - kfree(newmem); + kvfree(newmem); return -EFAULT; } oldmem = d->memory; @@ -712,7 +725,7 @@ static long vhost_set_memory(struct vhost_dev *d, struct vhost_memory __user *m) d->vqs[i]->memory = newmem; mutex_unlock(&d->vqs[i]->mutex); } - kfree(oldmem); + kvfree(oldmem); return 0; } -- cgit v1.2.3 From c9ce42f72fd0ba180fd35539829e4139dca31494 Mon Sep 17 00:00:00 2001 From: Igor Mammedov Date: Thu, 2 Jul 2015 15:08:11 +0200 Subject: vhost: add max_mem_regions module parameter it became possible to use a bigger amount of memory slots, which is used by memory hotplug for registering hotplugged memory. However QEMU crashes if it's used with more than ~60 pc-dimm devices and vhost-net enabled since host kernel in module vhost-net refuses to accept more than 64 memory regions. Allow to tweak limit via max_mem_regions module paramemter with default value set to 64 slots. Signed-off-by: Igor Mammedov Signed-off-by: Michael S. Tsirkin --- drivers/vhost/vhost.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) (limited to 'drivers/vhost') diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c index a4ac369f6adb..a9fe859f43c8 100644 --- a/drivers/vhost/vhost.c +++ b/drivers/vhost/vhost.c @@ -30,8 +30,12 @@ #include "vhost.h" +static ushort max_mem_regions = 64; +module_param(max_mem_regions, ushort, 0444); +MODULE_PARM_DESC(max_mem_regions, + "Maximum number of memory regions in memory map. (default: 64)"); + enum { - VHOST_MEMORY_MAX_NREGIONS = 64, VHOST_MEMORY_F_LOG = 0x1, }; @@ -697,7 +701,7 @@ static long vhost_set_memory(struct vhost_dev *d, struct vhost_memory __user *m) return -EFAULT; if (mem.padding) return -EOPNOTSUPP; - if (mem.nregions > VHOST_MEMORY_MAX_NREGIONS) + if (mem.nregions > max_mem_regions) return -E2BIG; newmem = vhost_kvzalloc(size + mem.nregions * sizeof(*m->regions)); if (!newmem) -- cgit v1.2.3