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Re: [PATCH RFC 08/21] ramblock: Cache the length to do file mmap() on ra
From: |
Dr. David Alan Gilbert |
Subject: |
Re: [PATCH RFC 08/21] ramblock: Cache the length to do file mmap() on ramblocks |
Date: |
Mon, 23 Jan 2023 18:51:51 +0000 |
User-agent: |
Mutt/2.2.9 (2022-11-12) |
* Peter Xu (peterx@redhat.com) wrote:
> We do proper page size alignment for file backed mmap()s for ramblocks.
> Even if it's as simple as that, cache the value because it'll be used in
> multiple places.
>
> Since at it, drop size for file_ram_alloc() and just use max_length because
> that's always true for file-backed ramblocks.
Having a length previously called 'memory' was a bit odd!
> Signed-off-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
> ---
> include/exec/ramblock.h | 2 ++
> softmmu/physmem.c | 14 +++++++-------
> 2 files changed, 9 insertions(+), 7 deletions(-)
>
> diff --git a/include/exec/ramblock.h b/include/exec/ramblock.h
> index 76cd0812c8..3f31ce1591 100644
> --- a/include/exec/ramblock.h
> +++ b/include/exec/ramblock.h
> @@ -32,6 +32,8 @@ struct RAMBlock {
> ram_addr_t offset;
> ram_addr_t used_length;
> ram_addr_t max_length;
> + /* Only used for file-backed ramblocks */
> + ram_addr_t mmap_length;
> void (*resized)(const char*, uint64_t length, void *host);
> uint32_t flags;
> /* Protected by iothread lock. */
> diff --git a/softmmu/physmem.c b/softmmu/physmem.c
> index aa1a7466e5..b5be02f1cb 100644
> --- a/softmmu/physmem.c
> +++ b/softmmu/physmem.c
> @@ -1533,7 +1533,6 @@ static int file_ram_open(const char *path,
> }
>
> static void *file_ram_alloc(RAMBlock *block,
> - ram_addr_t memory,
> int fd,
> bool readonly,
> bool truncate,
> @@ -1563,14 +1562,14 @@ static void *file_ram_alloc(RAMBlock *block,
> }
> #endif
>
> - if (memory < block->page_size) {
> + if (block->max_length < block->page_size) {
> error_setg(errp, "memory size 0x" RAM_ADDR_FMT " must be equal to "
> "or larger than page size 0x%zx",
> - memory, block->page_size);
> + block->max_length, block->page_size);
> return NULL;
> }
>
> - memory = ROUND_UP(memory, block->page_size);
> + block->mmap_length = ROUND_UP(block->max_length, block->page_size);
>
> /*
> * ftruncate is not supported by hugetlbfs in older
> @@ -1586,7 +1585,7 @@ static void *file_ram_alloc(RAMBlock *block,
> * those labels. Therefore, extending the non-empty backend file
> * is disabled as well.
> */
> - if (truncate && ftruncate(fd, memory)) {
> + if (truncate && ftruncate(fd, block->mmap_length)) {
> perror("ftruncate");
> }
>
> @@ -1594,7 +1593,8 @@ static void *file_ram_alloc(RAMBlock *block,
> qemu_map_flags |= (block->flags & RAM_SHARED) ? QEMU_MAP_SHARED : 0;
> qemu_map_flags |= (block->flags & RAM_PMEM) ? QEMU_MAP_SYNC : 0;
> qemu_map_flags |= (block->flags & RAM_NORESERVE) ? QEMU_MAP_NORESERVE :
> 0;
> - area = qemu_ram_mmap(fd, memory, block->mr->align, qemu_map_flags,
> offset);
> + area = qemu_ram_mmap(fd, block->mmap_length, block->mr->align,
> + qemu_map_flags, offset);
> if (area == MAP_FAILED) {
> error_setg_errno(errp, errno,
> "unable to map backing store for guest RAM");
> @@ -2100,7 +2100,7 @@ RAMBlock *qemu_ram_alloc_from_fd(ram_addr_t size,
> MemoryRegion *mr,
> new_block->used_length = size;
> new_block->max_length = size;
> new_block->flags = ram_flags;
> - new_block->host = file_ram_alloc(new_block, size, fd, readonly,
> + new_block->host = file_ram_alloc(new_block, fd, readonly,
> !file_size, offset, errp);
> if (!new_block->host) {
> g_free(new_block);
> --
> 2.37.3
>
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK
- Re: [PATCH RFC 04/21] madvise: Include linux/mman.h under linux-headers/, (continued)
- [PATCH RFC 05/21] madvise: Add QEMU_MADV_SPLIT, Peter Xu, 2023/01/17
- [PATCH RFC 06/21] madvise: Add QEMU_MADV_COLLAPSE, Peter Xu, 2023/01/17
- [PATCH RFC 07/21] ramblock: Cache file offset for file-backed ramblocks, Peter Xu, 2023/01/17
- [PATCH RFC 08/21] ramblock: Cache the length to do file mmap() on ramblocks, Peter Xu, 2023/01/17
- [PATCH RFC 01/21] update linux headers, Peter Xu, 2023/01/17
- [PATCH RFC 10/21] ramblock: Add ramblock_file_map(), Peter Xu, 2023/01/17
- Re: [PATCH RFC 10/21] ramblock: Add ramblock_file_map(), Juan Quintela, 2023/01/30