Re: [PATCH v4 13/15] util: oslib: Resizeable anonymous allocations under POSIX

["Murilo Opsfelder Araújo" <muriloo@linux.ibm.com>]

On Thursday, March 5, 2020 11:29:43 AM -03 David Hildenbrand wrote:
> Introduce qemu_anon_ram_alloc_resizeable() and qemu_anon_ram_resize().
> Implement them under POSIX and make them return NULL under WIN32.
>
> Under POSIX, we make use of resizeable mmaps. An implementation under
> WIN32 is theoretically possible AFAIK and can be added later.
>
> In qemu_anon_ram_free(), rename the size parameter to max_size, to make
> it clearer that we have to use the maximum size when freeing resizeable
> anonymous allocations.
>
> Reviewed-by: Peter Xu <peterx@redhat.com>
> Cc: Richard Henderson <rth@twiddle.net>
> Cc: Paolo Bonzini <pbonzini@redhat.com>
> Cc: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
> Cc: Eduardo Habkost <ehabkost@redhat.com>
> Cc: Marcel Apfelbaum <marcel.apfelbaum@gmail.com>
> Cc: Stefan Weil <sw@weilnetz.de>
> Cc: Igor Mammedov <imammedo@redhat.com>
> Signed-off-by: David Hildenbrand <david@redhat.com>
> ---

Acked-by: Murilo Opsfelder Araujo <muriloo@linux.ibm.com>

>  include/qemu/osdep.h |  6 +++++-
>  util/oslib-posix.c   | 37 ++++++++++++++++++++++++++++++++++---
>  util/oslib-win32.c   | 14 ++++++++++++++
>  util/trace-events    |  4 +++-
>  4 files changed, 56 insertions(+), 5 deletions(-)
>
> diff --git a/include/qemu/osdep.h b/include/qemu/osdep.h
> index 9bd3dcfd13..a1ea9e043d 100644
> --- a/include/qemu/osdep.h
> +++ b/include/qemu/osdep.h
> @@ -311,8 +311,12 @@ int qemu_daemon(int nochdir, int noclose);
>  void *qemu_try_memalign(size_t alignment, size_t size);
>  void *qemu_memalign(size_t alignment, size_t size);
>  void *qemu_anon_ram_alloc(size_t size, uint64_t *align, bool shared);
> +void *qemu_anon_ram_alloc_resizeable(size_t size, size_t max_size,
> +                                     uint64_t *align, bool shared);
> +bool qemu_anon_ram_resize(void *ptr, size_t old_size, size_t new_size,
> +                          bool shared);
>  void qemu_vfree(void *ptr);
> -void qemu_anon_ram_free(void *ptr, size_t size);
> +void qemu_anon_ram_free(void *ptr, size_t max_size);
>
>  #define QEMU_MADV_INVALID -1
>
> diff --git a/util/oslib-posix.c b/util/oslib-posix.c
> index 897e8f3ba6..34b1ce74b7 100644
> --- a/util/oslib-posix.c
> +++ b/util/oslib-posix.c
> @@ -223,16 +223,47 @@ void *qemu_anon_ram_alloc(size_t size, uint64_t
> *alignment, bool shared) return ptr;
>  }
>
> +void *qemu_anon_ram_alloc_resizeable(size_t size, size_t max_size,
> +                                     uint64_t *alignment, bool shared)
> +{
> +    size_t align = QEMU_VMALLOC_ALIGN;
> +    void *ptr = qemu_ram_mmap_resizeable(-1, size, max_size, align, shared,
> +                                         false);
> +
> +    if (ptr == MAP_FAILED) {
> +        return NULL;
> +    }
> +
> +    if (alignment) {
> +        *alignment = align;
> +    }
> +
> +    trace_qemu_anon_ram_alloc_resizeable(size, max_size, ptr);
> +    return ptr;
> +}
> +
> +bool qemu_anon_ram_resize(void *ptr, size_t old_size, size_t new_size,
> +                          bool shared)
> +{
> +    bool resized = qemu_ram_mmap_resize(ptr, -1, old_size, new_size,
> shared, +                                        false);
> +
> +    if (resized) {
> +        trace_qemu_anon_ram_resize(old_size, new_size, ptr);
> +    }
> +    return resized;
> +}
> +
>  void qemu_vfree(void *ptr)
>  {
>      trace_qemu_vfree(ptr);
>      free(ptr);
>  }
>
> -void qemu_anon_ram_free(void *ptr, size_t size)
> +void qemu_anon_ram_free(void *ptr, size_t max_size)
>  {
> -    trace_qemu_anon_ram_free(ptr, size);
> -    qemu_ram_munmap(-1, ptr, size);
> +    trace_qemu_anon_ram_free(ptr, max_size);
> +    qemu_ram_munmap(-1, ptr, max_size);
>  }
>
>  void qemu_set_block(int fd)
> diff --git a/util/oslib-win32.c b/util/oslib-win32.c
> index e9b14ab178..c034fdfe01 100644
> --- a/util/oslib-win32.c
> +++ b/util/oslib-win32.c
> @@ -90,6 +90,20 @@ void *qemu_anon_ram_alloc(size_t size, uint64_t *align,
> bool shared) return ptr;
>  }
>
> +void *qemu_anon_ram_alloc_resizeable(size_t size, size_t max_size,
> +                                     uint64_t *align, bool shared)
> +{
> +    /* resizeable ram not implemented yet */
> +    return NULL;
> +}
> +
> +bool qemu_anon_ram_resize(void *ptr, size_t old_size, size_t new_size,
> +                          bool shared)
> +{
> +    /* resizeable ram not implemented yet */
> +    return false;
> +}
> +
>  void qemu_vfree(void *ptr)
>  {
>      trace_qemu_vfree(ptr);
> diff --git a/util/trace-events b/util/trace-events
> index a4d39eca5e..24a6f1a1e1 100644
> --- a/util/trace-events
> +++ b/util/trace-events
> @@ -46,8 +46,10 @@ qemu_co_mutex_unlock_return(void *mutex, void *self)
> "mutex %p self %p" # oslib-posix.c
>  qemu_memalign(size_t alignment, size_t size, void *ptr) "alignment %zu size
> %zu ptr %p" qemu_anon_ram_alloc(size_t size, void *ptr) "size %zu ptr %p"
> +qemu_anon_ram_alloc_resizeable(size_t size, size_t max_size, void *ptr)
> "size %zu max_size %zu ptr %p" +qemu_anon_ram_resize(size_t old_size,
> size_t new_size, void *ptr) "old_size %zu new_size %zu ptr %p"
> qemu_vfree(void *ptr) "ptr %p"
> -qemu_anon_ram_free(void *ptr, size_t size) "ptr %p size %zu"
> +qemu_anon_ram_free(void *ptr, size_t max_size) "ptr %p max_size %zu"
>
>  # hbitmap.c
>  hbitmap_iter_skip_words(const void *hb, void *hbi, uint64_t pos, unsigned
> long cur) "hb %p hbi %p pos %"PRId64" cur 0x%lx"


--
Murilo