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

[Max Reitz <mreitz@redhat.com>]

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On 08.10.19 11:15, 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

Sounds good to me.

Max


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