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Re: [Qemu-devel] [PATCH v1 2/2] migration: add bitmap for copied page
From: |
Juan Quintela |
Subject: |
Re: [Qemu-devel] [PATCH v1 2/2] migration: add bitmap for copied page |
Date: |
Tue, 13 Jun 2017 13:42:02 +0200 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/25.2 (gnu/linux) |
Alexey Perevalov <address@hidden> wrote:
Hi
I think that it would make things clearer if we do a s/copied/received/
As what we are tracking here are the pages that have already been
received.
> This patch adds ability to track down already copied
> pages, it's necessary for calculation vCPU block time in
> postcopy migration feature, maybe for restore after
> postcopy migration failure.
> Also it's necessary to solve shared memory issue in
> postcopy livemigration. Information about copied pages
> will be transferred to the software virtual bridge
> (e.g. OVS-VSWITCHD), to avoid fallocate (unmap) for
> already copied pages. fallocate syscall is required for
> remmaped shared memory, due to remmaping itself blocks
> ioctl(UFFDIO_COPY, ioctl in this case will end with EEXIT
> error (struct page is exists after remmap).
>
> Bitmap is placed into RAMBlock as another postcopy/precopy
> related bitmaps.
Why are we not using the TARGET_PAGE_SIZE as units of the bitmap?
> copied bitmap is not releasing due to ramblocks is not releasing
> too.
RAMBlocks are used for other reasons, not only migration. This bitmaps
can be released on the ram_load_cleanup() function. See my patches on
list about how to use it.
> Signed-off-by: Alexey Perevalov <address@hidden>
> ---
> include/exec/ram_addr.h | 3 +++
> include/migration/migration.h | 3 +++
> migration/postcopy-ram.c | 7 ++++++
> migration/ram.c | 54
> ++++++++++++++++++++++++++++++++++++++++++-
> migration/ram.h | 5 ++++
> migration/savevm.c | 1 +
> 6 files changed, 72 insertions(+), 1 deletion(-)
>
> diff --git a/include/exec/ram_addr.h b/include/exec/ram_addr.h
> index 140efa8..56cdf16 100644
> --- a/include/exec/ram_addr.h
> +++ b/include/exec/ram_addr.h
> @@ -47,6 +47,9 @@ struct RAMBlock {
> * of the postcopy phase
> */
> unsigned long *unsentmap;
> + /* bitmap of already copied pages in postcopy */
/* bitmap of already received pages */
Why do we want to use it only for postcopy? And not in the general case?
> + unsigned long *copiedmap;
unsigned long *receivedmap;
> + size_t nr_copiedmap;
I think we don't need it, just use on its only use:
rb->max_length >> qemu_page_target_bits()?
> };
>
> static inline bool offset_in_ramblock(RAMBlock *b, ram_addr_t offset)
> diff --git a/include/migration/migration.h b/include/migration/migration.h
> index 79b5484..8005c11 100644
> --- a/include/migration/migration.h
> +++ b/include/migration/migration.h
> @@ -226,4 +226,7 @@ void savevm_skip_configuration(void);
> int global_state_store(void);
> void global_state_store_running(void);
>
> +size_t get_copiedmap_size(RAMBlock *rb);
> +void movecopiedmap(void *dst, RAMBlock *rb, size_t len);
> +
> #endif
After my last PULL Request, this needs to be into:
include/migration/misc.h
And we can rename the functions to:
size_t received_map_pages(RAMBlock *rb);
void received_map_copy(void *dst, RAMBlock *rb, size_t len);
> diff --git a/migration/postcopy-ram.c b/migration/postcopy-ram.c
> index f6244ee..e13b22e 100644
> --- a/migration/postcopy-ram.c
> +++ b/migration/postcopy-ram.c
> @@ -576,6 +576,13 @@ int postcopy_place_page(MigrationIncomingState *mis,
> void *host, void *from,
> copy_struct.len = pagesize;
> copy_struct.mode = 0;
>
> +
> + /* copied page isn't feature of blocktime calculation,
> + * it's more general entity, so keep it here,
> + * but gup betwean two following operation could be high,
> + * and in this case blocktime for such small interval will be lost */
> + set_copiedmap_by_addr(host, rb);
>
> /* copy also acks to the kernel waking the stalled thread up
> * TODO: We can inhibit that ack and only do it if it was requested
> * which would be slightly cheaper, but we'd have to be careful
> diff --git a/migration/ram.c b/migration/ram.c
> index 4ed7c2c..8466e59 100644
> --- a/migration/ram.c
> +++ b/migration/ram.c
> @@ -149,6 +149,58 @@ out:
> return ret;
> }
>
> +void init_copiedmap(void)
received_map_init(void);
> +{
> + RAMBlock *rb;
> + RAMBLOCK_FOREACH(rb) {
> + unsigned long pages;
> + pages = rb->max_length >> find_first_bit(&rb->page_size,
> + 8 * sizeof(rb->page_size));
> + /* need for destination, bitmap_new calls
> + * g_try_malloc0 and this function
> + * Attempts to allocate @n_bytes, initialized to 0'sh */
> + rb->copiedmap = bitmap_new(pages);
> + rb->nr_copiedmap = pages;
> + }
> +}
> +
> +static unsigned long int get_copied_bit_offset(void *host_addr,
> RAMBlock *rb)
received_map_get_offset(...)
> +{
> + uint64_t host_addr_offset = (uint64_t)(uintptr_t)(host_addr
> +
> + int page_shift = find_first_bit(&rb->page_size, 8 *
> sizeof(rb->page_size));
with my suggesiton this becomes:
uint64_t offset = (uint64_t)(uintptr_t)(host_addr - (void *)rb->host);
return offset >> qemu_target_page_bits();
I wonder that we don't have a function to pass an absolute address to an
relative page :p
> +int test_copiedmap_by_addr(void *host_addr, RAMBlock *rb)
int receive_map_test_addr(...) ?
> +{
> + return test_bit(get_copied_bit_offset(host_addr, rb), rb->copiedmap);
> +}
> +
> +void set_copiedmap_by_addr(void *host_addr, RAMBlock *rb)
void receive_map_set_addr()
> @@ -1852,11 +1904,11 @@ int ram_discard_range(const char *rbname, uint64_t
> start, size_t length)
> {
> int ret = -1;
>
> - trace_ram_discard_range(rbname, start, length);
>
> rcu_read_lock();
> RAMBlock *rb = qemu_ram_block_by_name(rbname);
>
> + trace_ram_discard_range(rbname, start, length);
Why is that bit included in this patch? I think this is independent of
the rest of the patch, no?
Thanks for the effort.
Later, Juan.
- [Qemu-devel] [PATCH v1 0/2] Add bitmap for copied pages in postcopy migration, Alexey Perevalov, 2017/06/13
- Message not available
- Message not available
- Re: [Qemu-devel] [PATCH v1 2/2] migration: add bitmap for copied page, Peter Xu, 2017/06/14
- Re: [Qemu-devel] [PATCH v1 2/2] migration: add bitmap for copied page, Alexey Perevalov, 2017/06/14
- Re: [Qemu-devel] [PATCH v1 2/2] migration: add bitmap for copied page, Peter Xu, 2017/06/14
- Re: [Qemu-devel] [PATCH v1 2/2] migration: add bitmap for copied page, Alexey Perevalov, 2017/06/14