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Re: [Qemu-devel] [PATCH] migration: cache memory region ram ptr
From: |
Peter Lieven |
Subject: |
Re: [Qemu-devel] [PATCH] migration: cache memory region ram ptr |
Date: |
Sat, 10 May 2014 18:44:19 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.4.0 |
or even this:
diff --git a/include/exec/memory.h b/include/exec/memory.h
index 1d55ad9..3003875 100644
--- a/include/exec/memory.h
+++ b/include/exec/memory.h
@@ -161,6 +161,7 @@ struct MemoryRegion {
unsigned ioeventfd_nb;
MemoryRegionIoeventfd *ioeventfds;
NotifierList iommu_notify;
+ void *ram_ptr;
};
/**
diff --git a/memory.c b/memory.c
index 3f1df23..6c1e413 100644
--- a/memory.c
+++ b/memory.c
@@ -862,6 +862,7 @@ void memory_region_init(MemoryRegion *mr,
mr->ioeventfd_nb = 0;
mr->ioeventfds = NULL;
mr->flush_coalesced_mmio = false;
+ mr->ram_ptr = NULL;
}
static uint64_t unassigned_mem_read(void *opaque, hwaddr addr,
@@ -1241,17 +1242,23 @@ void memory_region_reset_dirty(MemoryRegion *mr, hwaddr
addr,
cpu_physical_memory_reset_dirty(mr->ram_addr + addr, size, client);
}
-void *memory_region_get_ram_ptr(MemoryRegion *mr)
+static void *memory_region_get_ram_ptr2(MemoryRegion *mr)
{
if (mr->alias) {
return memory_region_get_ram_ptr(mr->alias) + mr->alias_offset;
}
-
assert(mr->terminates);
-
return qemu_get_ram_ptr(mr->ram_addr & TARGET_PAGE_MASK);
}
+inline void *memory_region_get_ram_ptr(MemoryRegion *mr)
+{
+ if (!mr->ram_ptr) {
+ mr->ram_ptr = memory_region_get_ram_ptr2(mr);
+ }
+ return mr->ram_ptr;
+}
+
static void memory_region_update_coalesced_range_as(MemoryRegion *mr,
AddressSpace *as)
{
FlatView *view;
Am 10.05.2014 18:32, schrieb Peter Lieven:
> Am 10.05.2014 17:33, schrieb Paolo Bonzini:
>> Il 10/05/2014 12:51, Peter Lieven ha scritto:
>>> we currently look up the ram ptr for each single page. Cache
>>> the pointer while we operate on the same block.
>> Why don't you instead cache the result in the MemoryRegion, so that
>> memory_region_get_ram_ptr becomes a simple, inline field access?
> This seems to work. Wondering if it has other side implications. Basic tests
> like booting vServers and migration work. What about XEN?
>
> diff --git a/include/exec/memory.h b/include/exec/memory.h
> index 1d55ad9..3003875 100644
> --- a/include/exec/memory.h
> +++ b/include/exec/memory.h
> @@ -161,6 +161,7 @@ struct MemoryRegion {
> unsigned ioeventfd_nb;
> MemoryRegionIoeventfd *ioeventfds;
> NotifierList iommu_notify;
> + void *ram_ptr;
> };
>
> /**
> diff --git a/memory.c b/memory.c
> index 3f1df23..78d4032 100644
> --- a/memory.c
> +++ b/memory.c
> @@ -862,6 +862,7 @@ void memory_region_init(MemoryRegion *mr,
> mr->ioeventfd_nb = 0;
> mr->ioeventfds = NULL;
> mr->flush_coalesced_mmio = false;
> + mr->ram_ptr = NULL;
> }
>
> static uint64_t unassigned_mem_read(void *opaque, hwaddr addr,
> @@ -1249,7 +1250,12 @@ void *memory_region_get_ram_ptr(MemoryRegion *mr)
>
> assert(mr->terminates);
>
> - return qemu_get_ram_ptr(mr->ram_addr & TARGET_PAGE_MASK);
> + if (mr->ram_ptr) {
> + return mr->ram_ptr;
> + }
> +
> + mr->ram_ptr = qemu_get_ram_ptr(mr->ram_addr & TARGET_PAGE_MASK);
> + return mr->ram_ptr;
> }
>
> static void memory_region_update_coalesced_range_as(MemoryRegion *mr,
> AddressSpace *as)
>
>
> Peter
>
>> Paolo
>>
>>> Signed-off-by: Peter Lieven <address@hidden>
>>> ---
>>> arch_init.c | 23 ++++++++++++++++-------
>>> 1 file changed, 16 insertions(+), 7 deletions(-)
>>>
>>> diff --git a/arch_init.c b/arch_init.c
>>> index 582b716..ce338aa 100644
>>> --- a/arch_init.c
>>> +++ b/arch_init.c
>>> @@ -594,13 +594,19 @@ static int ram_save_block(QEMUFile *f, bool
>>> last_stage)
>>> ram_bulk_stage = false;
>>> }
>>> } else {
>>> + static uint8_t *ram_ptr;
>>> int ret;
>>> uint8_t *p;
>>> bool send_async = true;
>>> - int cont = (block == last_sent_block) ?
>>> - RAM_SAVE_FLAG_CONTINUE : 0;
>>> + int cont = 0;
>>>
>>> - p = memory_region_get_ram_ptr(mr) + offset;
>>> + if (block != last_sent_block) {
>>> + ram_ptr = memory_region_get_ram_ptr(mr);
>>> + } else {
>>> + cont = RAM_SAVE_FLAG_CONTINUE;
>>> + }
>>> +
>>> + p = ram_ptr + offset;
>>>
>>> /* In doubt sent page as normal */
>>> bytes_sent = -1;
>>> @@ -990,16 +996,17 @@ static inline void *host_from_stream_offset(QEMUFile
>>> *f,
>>> int flags)
>>> {
>>> static RAMBlock *block = NULL;
>>> + static uint8_t *ram_ptr;
>>> char id[256];
>>> uint8_t len;
>>>
>>> if (flags & RAM_SAVE_FLAG_CONTINUE) {
>>> - if (!block) {
>>> + if (!block || !ram_ptr) {
>>> fprintf(stderr, "Ack, bad migration stream!\n");
>>> return NULL;
>>> }
>>>
>>> - return memory_region_get_ram_ptr(block->mr) + offset;
>>> + return ram_ptr + offset;
>>> }
>>>
>>> len = qemu_get_byte(f);
>>> @@ -1007,8 +1014,10 @@ static inline void *host_from_stream_offset(QEMUFile
>>> *f,
>>> id[len] = 0;
>>>
>>> QTAILQ_FOREACH(block, &ram_list.blocks, next) {
>>> - if (!strncmp(id, block->idstr, sizeof(id)))
>>> - return memory_region_get_ram_ptr(block->mr) + offset;
>>> + if (!strncmp(id, block->idstr, sizeof(id))) {
>>> + ram_ptr = memory_region_get_ram_ptr(block->mr);
>>> + return ram_ptr + offset;
>>> + }
>>> }
>>>
>>> fprintf(stderr, "Can't find block %s!\n", id);
>>>