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Re: [PATCH v3 07/10] block/dirty-bitmap: improve _next_dirty_area API
From: |
Vladimir Sementsov-Ogievskiy |
Subject: |
Re: [PATCH v3 07/10] block/dirty-bitmap: improve _next_dirty_area API |
Date: |
Mon, 20 Jan 2020 16:26:00 +0000 |
20.01.2020 16:58, Max Reitz wrote:
> On 19.12.19 11:03, Vladimir Sementsov-Ogievskiy wrote:
>> Firstly, _next_dirty_area is for scenarios when we may contiguously
>> search for next dirty area inside some limited region, so it is more
>> comfortable to specify "end" which should not be recalculated on each
>> iteration.
>>
>> Secondly, let's add a possibility to limit resulting area size, not
>> limiting searching area. This will be used in NBD code in further
>> commit. (Note that now bdrv_dirty_bitmap_next_dirty_area is unused)
>>
>> Signed-off-by: Vladimir Sementsov-Ogievskiy <address@hidden>
>> ---
>> include/block/dirty-bitmap.h | 3 ++-
>> include/qemu/hbitmap.h | 25 ++++++++++++---------
>> block/dirty-bitmap.c | 6 +++--
>> tests/test-hbitmap.c | 43 +++++++++++++++++++++++-------------
>> util/hbitmap.c | 41 +++++++++++++++++++++-------------
>> 5 files changed, 74 insertions(+), 44 deletions(-)
>
> [...]
>
>> /**
>> diff --git a/tests/test-hbitmap.c b/tests/test-hbitmap.c
>> index e3f1b3f361..d75e84a76a 100644
>> --- a/tests/test-hbitmap.c
>> +++ b/tests/test-hbitmap.c
>> @@ -920,18 +920,19 @@ static void
>> test_hbitmap_next_x_after_truncate(TestHBitmapData *data,
>> test_hbitmap_next_x_check(data, 0);
>> }
>>
>> -static void test_hbitmap_next_dirty_area_check(TestHBitmapData *data,
>> - int64_t offset,
>> - int64_t count)
>> +static void test_hbitmap_next_dirty_area_check_limited(TestHBitmapData
>> *data,
>> + int64_t offset,
>> + int64_t count,
>> + int64_t max_dirty)
>> {
>> int64_t off1, off2;
>> int64_t len1 = 0, len2;
>> bool ret1, ret2;
>> int64_t end;
>>
>> - off1 = offset;
>> - len1 = count;
>> - ret1 = hbitmap_next_dirty_area(data->hb, &off1, &len1);
>> + ret1 = hbitmap_next_dirty_area(data->hb,
>> + offset, count == INT64_MAX ? INT64_MAX : offset + count,
>> max_dirty,
>> + &off1, &len1);
>>
>> end = offset > data->size || data->size - offset < count ? data->size :
>> offset +
>> count;
>> @@ -940,21 +941,25 @@ static void
>> test_hbitmap_next_dirty_area_check(TestHBitmapData *data,
>> ;
>
> These empty statements look a bit weird to me. But they’re
> pre-existing, obviously.
>
>> }
>>
>> - for (len2 = 1; off2 + len2 < end && hbitmap_get(data->hb, off2 + len2);
>> - len2++) {
>> + for (len2 = 1; (off2 + len2 < end && len2 < max_dirty &&
>> + hbitmap_get(data->hb, off2 + len2)); len2++)
>> + {
>> ;
>> }
>
> [...]
>
>> diff --git a/util/hbitmap.c b/util/hbitmap.c
>> index d23f4b9678..2a1661ec1d 100644
>> --- a/util/hbitmap.c
>> +++ b/util/hbitmap.c
>> @@ -270,22 +270,34 @@ int64_t hbitmap_next_zero(const HBitmap *hb, int64_t
>> start, int64_t count)
>> return res;
>> }
>>
>> -bool hbitmap_next_dirty_area(const HBitmap *hb, int64_t *start, int64_t
>> *count)
>> +bool hbitmap_next_dirty_area(const HBitmap *hb, int64_t start, int64_t end,
>> + int64_t max_dirty_count,
>> + int64_t *dirty_start, int64_t *dirty_count)
>> {
>> - int64_t area_start, area_end;
>> + int64_t next_zero;
>>
>> - area_start = hbitmap_next_dirty(hb, *start, *count);
>> - if (area_start < 0) {
>> + assert(start >= 0 && end >= 0 && max_dirty_count > 0);
>> +
>> + if (start >= hb->orig_size || end <= start) {
>> + return false;
>> + }
>> +
>> + end = MIN(end, hb->orig_size);
>
> You could put this assignment before the if () and then drop the “start”
> check from the condition. (But that’s mostly me itching to do
> optimizations. I don’t think it’d make the code easier to read.)
>
> [...]
>
>> @@ -844,13 +856,12 @@ static void hbitmap_sparse_merge(HBitmap *dst, const
>> HBitmap *src)
>> int64_t offset = 0;
>> int64_t count = src->orig_size;
>
> These initializations are now unnecessary. I’d drop them because I find
> at least the one for @count a tiny bit confusing now. (Because as a
> reader, I’d wonder where this value is used.)
>
> With that done (or maybe not because you disagree):
I agree)
>
> Reviewed-by: Max Reitz <address@hidden>
>
>>
>> - while (hbitmap_next_dirty_area(src, &offset, &count)) {
>> + for (offset = 0;
>> + hbitmap_next_dirty_area(src, offset, src->orig_size, INT64_MAX,
>> + &offset, &count);
>> + offset += count)
>> + {
>> hbitmap_set(dst, offset, count);
>> - offset += count;
>> - if (offset >= src->orig_size) {
>> - break;
>> - }
>> - count = src->orig_size - offset;
>> }
>> }
>>
>>
>
--
Best regards,
Vladimir