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Re: [Qemu-devel] [PATCH] qcow2: allocate cluster_cache/cluster_data on d
From: |
Alexey Kardashevskiy |
Subject: |
Re: [Qemu-devel] [PATCH] qcow2: allocate cluster_cache/cluster_data on demand |
Date: |
Thu, 31 Aug 2017 10:03:00 +1000 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.2.1 |
On 31/08/17 03:20, Stefan Hajnoczi wrote:
> On Tue, Aug 22, 2017 at 02:56:00PM +1000, Alexey Kardashevskiy wrote:
>> On 19/08/17 12:46, Alexey Kardashevskiy wrote:
>>> On 19/08/17 01:18, Eric Blake wrote:
>>>> On 08/18/2017 08:31 AM, Stefan Hajnoczi wrote:
>>>>> Most qcow2 files are uncompressed so it is wasteful to allocate (32 + 1)
>>>>> * cluster_size + 512 bytes upfront. Allocate s->cluster_cache and
>>>>> s->cluster_data when the first read operation is performance on a
>>>>> compressed cluster.
>>>>>
>>>>> The buffers are freed in .bdrv_close(). .bdrv_open() no longer has any
>>>>> code paths that can allocate these buffers, so remove the free functions
>>>>> in the error code path.
>>>>>
>>>>> Reported-by: Alexey Kardashevskiy <address@hidden>
>>>>> Cc: Kevin Wolf <address@hidden>
>>>>> Signed-off-by: Stefan Hajnoczi <address@hidden>
>>>>> ---
>>>>> Alexey: Does this improve your memory profiling results?
>>>>
>>>> Is this a regression from earlier versions?
>>>
>>> Hm, I have not thought about this.
>>>
>>> So. I did bisect and this started happening from
>>> 9a4c0e220d8a4f82b5665d0ee95ef94d8e1509d5
>>> "hw/virtio-pci: fix virtio behaviour"
>>>
>>> Before that, the very same command line would take less than 1GB of
>>> resident memory. That thing basically enforces virtio-1.0 for QEMU <=2.6
>>> which means that upstream with "-machine pseries-2.6" works fine (less than
>>> 1GB), "-machine pseries-2.7" does not (close to 7GB, sometime even 9GB).
>>>
>>> Then I tried bisecting again, with
>>> "scsi=off,disable-modern=off,disable-legacy=on" on my 150 virtio-block
>>> devices, started from
>>> e266d421490e0 "virtio-pci: add flags to enable/disable legacy/modern" (it
>>> added the disable-modern switch) which uses 2GB of memory.
>>>
>>> I ended up with ada434cd0b44 "virtio-pci: implement cfg capability".
>>>
>>> Then I removed proxy->modern_as on v2.10.0-rc3 (see below) and got 1.5GB of
>>> used memory (yay!)
>>>
>>> I do not really know how to reinterpret all of this, do you?
>>
>>
>> Anyone, ping? Should I move the conversation to the original thread? Any
>> hacks to try with libc?
>
> I suggest a new top-level thread with Michael Tsirkin CCed.
I am continuing in the original "Memory use with >100 virtio devices"
thread and the problem is more generic than virtio, it is just easier to
reproduce it with virtio, that's all.
--
Alexey
Re: [Qemu-devel] [PATCH] qcow2: allocate cluster_cache/cluster_data on demand, Stefan Hajnoczi, 2017/08/21
Re: [Qemu-devel] [PATCH] qcow2: allocate cluster_cache/cluster_data on demand, Alexey Kardashevskiy, 2017/08/18