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Re: [Qemu-devel] [PATCH v3 24/29] bitmap: add atomic test and clear
From: |
Fam Zheng |
Subject: |
Re: [Qemu-devel] [PATCH v3 24/29] bitmap: add atomic test and clear |
Date: |
Wed, 27 May 2015 16:05:45 +0800 |
User-agent: |
Mutt/1.5.23 (2014-03-12) |
On Tue, 05/26 18:55, Paolo Bonzini wrote:
> From: Stefan Hajnoczi <address@hidden>
>
> The new bitmap_test_and_clear_atomic() function clears a range and
> returns whether or not the bits were set.
>
> Signed-off-by: Stefan Hajnoczi <address@hidden>
> Message-Id: <address@hidden>
> [Test before xchg; then a full barrier is needed at the end just like
> in the previous patch. The barrier can be avoided if we did at least
> one xchg. - Paolo]
> Signed-off-by: Paolo Bonzini <address@hidden>
Reviewed-by: Fam Zheng <address@hidden>
> ---
> include/qemu/bitmap.h | 2 ++
> util/bitmap.c | 45 +++++++++++++++++++++++++++++++++++++++++++++
> 2 files changed, 47 insertions(+)
>
> diff --git a/include/qemu/bitmap.h b/include/qemu/bitmap.h
> index 3e0a4f3..86dd9cd 100644
> --- a/include/qemu/bitmap.h
> +++ b/include/qemu/bitmap.h
> @@ -41,6 +41,7 @@
> * bitmap_set(dst, pos, nbits) Set specified bit area
> * bitmap_set_atomic(dst, pos, nbits) Set specified bit area with atomic
> ops
> * bitmap_clear(dst, pos, nbits) Clear specified bit area
> + * bitmap_test_and_clear_atomic(dst, pos, nbits) Test and clear area
> * bitmap_find_next_zero_area(buf, len, pos, n, mask) Find bit free
> area
> */
>
> @@ -229,6 +230,7 @@ static inline int bitmap_intersects(const unsigned long
> *src1,
> void bitmap_set(unsigned long *map, long i, long len);
> void bitmap_set_atomic(unsigned long *map, long i, long len);
> void bitmap_clear(unsigned long *map, long start, long nr);
> +bool bitmap_test_and_clear_atomic(unsigned long *map, long start, long nr);
> unsigned long bitmap_find_next_zero_area(unsigned long *map,
> unsigned long size,
> unsigned long start,
> diff --git a/util/bitmap.c b/util/bitmap.c
> index 39994af..300a68e 100644
> --- a/util/bitmap.c
> +++ b/util/bitmap.c
> @@ -235,6 +235,51 @@ void bitmap_clear(unsigned long *map, long start, long
> nr)
> }
> }
>
> +bool bitmap_test_and_clear_atomic(unsigned long *map, long start, long nr)
> +{
> + unsigned long *p = map + BIT_WORD(start);
> + const long size = start + nr;
> + int bits_to_clear = BITS_PER_LONG - (start % BITS_PER_LONG);
> + unsigned long mask_to_clear = BITMAP_FIRST_WORD_MASK(start);
> + unsigned long dirty = 0;
> + unsigned long old_bits;
> +
> + /* First word */
> + if (nr - bits_to_clear > 0) {
> + old_bits = atomic_fetch_and(p, ~mask_to_clear);
> + dirty |= old_bits & mask_to_clear;
> + nr -= bits_to_clear;
> + bits_to_clear = BITS_PER_LONG;
> + mask_to_clear = ~0UL;
> + p++;
> + }
> +
> + /* Full words */
> + if (bits_to_clear == BITS_PER_LONG) {
> + while (nr >= BITS_PER_LONG) {
> + if (*p) {
> + old_bits = atomic_xchg(p, 0);
> + dirty |= old_bits;
> + }
> + nr -= BITS_PER_LONG;
> + p++;
> + }
> + }
> +
> + /* Last word */
> + if (nr) {
> + mask_to_clear &= BITMAP_LAST_WORD_MASK(size);
> + old_bits = atomic_fetch_and(p, ~mask_to_clear);
> + dirty |= old_bits & mask_to_clear;
> + } else {
> + if (!dirty) {
> + smp_mb();
> + }
> + }
> +
> + return dirty != 0;
> +}
> +
> #define ALIGN_MASK(x,mask) (((x)+(mask))&~(mask))
>
> /**
> --
> 1.8.3.1
>
>
>
- [Qemu-devel] [PATCH v3 15/29] exec: move functions to translate-all.h, (continued)
- [Qemu-devel] [PATCH v3 15/29] exec: move functions to translate-all.h, Paolo Bonzini, 2015/05/26
- [Qemu-devel] [PATCH v3 23/29] bitmap: add atomic set functions, Paolo Bonzini, 2015/05/26
- [Qemu-devel] [PATCH v3 19/29] exec: pass client mask to cpu_physical_memory_set_dirty_range, Paolo Bonzini, 2015/05/26
- [Qemu-devel] [PATCH v3 07/29] framebuffer: check memory_region_is_logging, Paolo Bonzini, 2015/05/26
- [Qemu-devel] [PATCH v3 11/29] memory: include DIRTY_MEMORY_MIGRATION in the dirty log mask, Paolo Bonzini, 2015/05/26
- [Qemu-devel] [PATCH v3 16/29] translate-all: remove unnecessary argument to tb_invalidate_phys_range, Paolo Bonzini, 2015/05/26
- [Qemu-devel] [PATCH v3 21/29] exec: only check relevant bitmaps for cleanliness, Paolo Bonzini, 2015/05/26
- [Qemu-devel] [PATCH v3 24/29] bitmap: add atomic test and clear, Paolo Bonzini, 2015/05/26
- Re: [Qemu-devel] [PATCH v3 24/29] bitmap: add atomic test and clear,
Fam Zheng <=
- [Qemu-devel] [PATCH v3 14/29] exec: use memory_region_get_dirty_log_mask to optimize dirty tracking, Paolo Bonzini, 2015/05/26
- [Qemu-devel] [PATCH v3 25/29] memory: use atomic ops for setting dirty memory bits, Paolo Bonzini, 2015/05/26
- [Qemu-devel] [PATCH v3 06/29] memory: prepare for multiple bits in the dirty log mask, Paolo Bonzini, 2015/05/26
- [Qemu-devel] [PATCH v3 17/29] cputlb: remove useless arguments to tlb_unprotect_code_phys, rename, Paolo Bonzini, 2015/05/26
- [Qemu-devel] [PATCH v3 26/29] migration: move dirty bitmap sync to ram_addr.h, Paolo Bonzini, 2015/05/26
- [Qemu-devel] [PATCH v3 12/29] kvm: remove special handling of DIRTY_MEMORY_MIGRATION in the dirty log mask, Paolo Bonzini, 2015/05/26
- [Qemu-devel] [PATCH v3 08/29] ui/console: remove dpy_gfx_update_dirty, Paolo Bonzini, 2015/05/26
- [Qemu-devel] [PATCH v3 27/29] memory: replace cpu_physical_memory_reset_dirty() with test-and-clear, Paolo Bonzini, 2015/05/26