Re: [PATCH 5/6] block/block-copy: add memory limit

[Max Reitz <mreitz@redhat.com>]

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On 08.10.19 11:20, Vladimir Sementsov-Ogievskiy wrote:
> 08.10.2019 12:15, Vladimir Sementsov-Ogievskiy wrote:
>> 08.10.2019 12:03, Max Reitz wrote:
>>> On 07.10.19 19:10, Vladimir Sementsov-Ogievskiy wrote:
>>>> 07.10.2019 18:27, Max Reitz wrote:
>>>>> On 03.10.19 19:15, Vladimir Sementsov-Ogievskiy wrote:
>>>>>> Currently total allocation for parallel requests to block-copy instance
>>>>>> is unlimited. Let's limit it to 128 MiB.
>>>>>>
>>>>>> For now block-copy is used only in backup, so actually we limit total
>>>>>> allocation for backup job.
>>>>>>
>>>>>> Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
>>>>>> ---
>>>>>>    include/block/block-copy.h | 3 +++
>>>>>>    block/block-copy.c         | 5 +++++
>>>>>>    2 files changed, 8 insertions(+)
>>>>>>
>>>>>> diff --git a/include/block/block-copy.h b/include/block/block-copy.h
>>>>>> index e2e135ff1b..bb666e7068 100644
>>>>>> --- a/include/block/block-copy.h
>>>>>> +++ b/include/block/block-copy.h
>>>>>> @@ -16,6 +16,7 @@
>>>>>>    #define BLOCK_COPY_H
>>>>>>    #include "block/block.h"
>>>>>> +#include "qemu/co-shared-amount.h"
>>>>>>    typedef struct BlockCopyInFlightReq {
>>>>>>        int64_t start_byte;
>>>>>> @@ -69,6 +70,8 @@ typedef struct BlockCopyState {
>>>>>>         */
>>>>>>        ProgressResetCallbackFunc progress_reset_callback;
>>>>>>        void *progress_opaque;
>>>>>> +
>>>>>> +    QemuCoSharedAmount *mem;
>>>>>>    } BlockCopyState;
>>>>>>    BlockCopyState *block_copy_state_new(BdrvChild *source, BdrvChild *target,
>>>>>> diff --git a/block/block-copy.c b/block/block-copy.c
>>>>>> index cc49d2345d..e700c20d0f 100644
>>>>>> --- a/block/block-copy.c
>>>>>> +++ b/block/block-copy.c
>>>>>> @@ -21,6 +21,7 @@
>>>>>>    #include "qemu/units.h"
>>>>>>    #define BLOCK_COPY_MAX_COPY_RANGE (16 * MiB)
>>>>>> +#define BLOCK_COPY_MAX_MEM (128 * MiB)
>>>>>>    static void coroutine_fn block_copy_wait_inflight_reqs(BlockCopyState *s,
>>>>>>                                                           int64_t start,
>>>>>> @@ -64,6 +65,7 @@ void block_copy_state_free(BlockCopyState *s)
>>>>>>        }
>>>>>>        bdrv_release_dirty_bitmap(s->source->bs, s->copy_bitmap);
>>>>>> +    qemu_co_shared_amount_free(s->mem);
>>>>>>        g_free(s);
>>>>>>    }
>>>>>> @@ -95,6 +97,7 @@ BlockCopyState *block_copy_state_new(BdrvChild *source, BdrvChild *target,
>>>>>>            .cluster_size = cluster_size,
>>>>>>            .len = bdrv_dirty_bitmap_size(copy_bitmap),
>>>>>>            .write_flags = write_flags,
>>>>>> +        .mem = qemu_co_shared_amount_new(BLOCK_COPY_MAX_MEM),
>>>>>>        };
>>>>>>        s->copy_range_size = QEMU_ALIGN_DOWN(max_transfer, cluster_size),
>>>>>> @@ -316,7 +319,9 @@ int coroutine_fn block_copy(BlockCopyState *s,
>>>>>>            bdrv_reset_dirty_bitmap(s->copy_bitmap, start, chunk_end - start);
>>>>>> +        qemu_co_get_amount(s->mem, chunk_end - start);
>>>>>
>>>>> Now that I see it like this, maybe the name is too short.  This sounds
>>>>> like it was trying to get some amount of coroutines.
>>>>>
>>>>> Would “qemu_co_get_from_shared_amount” be too long?  (Something like
>>>>> qemu_co_sham_alloc() would be funny, but maybe not.  :-)  Or maybe
>>>>> exactly because it”s funny.)
>>>>>
>>>>
>>>> hmm sham may be interpreted as shared memory, not only like shame..
>>>
>>> “sham” is also a word by itself. :-)
>>
>> Hmm didn't know, me go to google translate. OK, sham looks a lot nicer than shame)
>>
>>>
>>>> And if we call it _alloc, the opposite should be _free, but how to
>>>> distinguish it from freeing the whole object? Hmm, use create/destroy for
>>>> the whole object maybe.
>>>>
>>>> May be, drop "qemu_" ? It's not very informative. Or may be drop "co_"?.
>>>>
>>>> I don't like shaming my shared amount :)
>>>
>>> It’s worse calling it all a sham.
>>>
>>>> May be, we should imagine, what are we allocating? May be balls?
>>>>
>>>> struct BallAllocator
>>>>
>>>> ball_allocator_create
>>>> ball_allocator_destroy
>>>>
>>>> co_try_alloc_balls
>>>> co_alloc_balls
>>>> co_free_balls
>>>>
>>>> Or bars? Or which thing may be used for funny naming and to not intersect
>>>> with existing concepts like memory?
>>>
>>> I love it (thanks for making my morning), but I fear it may be
>>> interpreted as risqué.
>>>
>>> Maybe just shres for shared resource?  So alloc_from_shres?
>>>
>>
>> OK for me. But.. How to name _free function than?
>>
>> struct SharedResource
>>
>> shres_create
>> shres_destroy
>>
>> co_try_alloc_from_shres
>> co_alloc_from_shres
>> co_free_???
>>
>> co_free_res_alloced_from_shres ? :)
>>
>> or
>>
>> co_try_get_from_shres
>> co_get_from_shres
>> co_put_to_shres
>>
> 
> 
> Another proposal from Roma: use "budget" word.

Instead of shres?  Why not.

Max


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