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Re: [PATCH] softmmu/physmem: Improve guest memory allocation failure err
From: |
Philippe Mathieu-Daudé |
Subject: |
Re: [PATCH] softmmu/physmem: Improve guest memory allocation failure error message |
Date: |
Mon, 23 Aug 2021 12:12:47 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.11.0 |
On 8/23/21 11:29 AM, David Hildenbrand wrote:
> On 23.08.21 11:23, Peter Maydell wrote:
>> On Mon, 23 Aug 2021 at 09:40, David Hildenbrand <david@redhat.com> wrote:
>>> Not opposed to printing the size, although I doubt that it will really
>>> stop similar questions/problems getting raised.
>>
>> The case that triggered this was somebody thinking
>> -m took a byte count, so very likely that an error message
>> saying "you tried to allocate 38TB" would have made their
>> mistake clear in a way that just "allocation failed" did not.
>> It also means that if a future user asks us for help then
>> we can look at the error message and immediately tell them
>> the problem, rather than going "hmm, what are all the possible
>> ways that allocation might have failed" and going off down
>> rabbitholes like VM overcommit settings...
>
> We've had similar issues recently where Linux memory overcommit handling
> rejected the allocation -- and the user was well aware about the actual
> size. You won't be able to catch such reports, because people don't
> understand how Linux memory overcommit handling works or was configured.
>
> "I have 3 GiB of free memory, why can't I create a 3 GiB VM". "I have 3
> GiB of RAM, why can't I create a 3 GiB VM even if it won't make use of
> all 3 GiB of memory".
>
> Thus my comment, it will only stop very basic usage issues. And I agree
> that looking at the error *might* help. It didn't help for the cases I
> just described, because we need much more system information to make a
> guess what the user error actually is.
Is it possible to get the maximal overcommitable amount on Linux?
- [PATCH] softmmu/physmem: Improve guest memory allocation failure error message, Philippe Mathieu-Daudé, 2021/08/20
- Re: [PATCH] softmmu/physmem: Improve guest memory allocation failure error message, David Hildenbrand, 2021/08/20
- Re: [PATCH] softmmu/physmem: Improve guest memory allocation failure error message, David Hildenbrand, 2021/08/23
- Re: [PATCH] softmmu/physmem: Improve guest memory allocation failure error message, Peter Maydell, 2021/08/23
- Re: [PATCH] softmmu/physmem: Improve guest memory allocation failure error message, David Hildenbrand, 2021/08/23
- Re: [PATCH] softmmu/physmem: Improve guest memory allocation failure error message,
Philippe Mathieu-Daudé <=
- Re: [PATCH] softmmu/physmem: Improve guest memory allocation failure error message, David Hildenbrand, 2021/08/23
- Re: [PATCH] softmmu/physmem: Improve guest memory allocation failure error message, Philippe Mathieu-Daudé, 2021/08/23
- Re: [PATCH] softmmu/physmem: Improve guest memory allocation failure error message, David Hildenbrand, 2021/08/23
- Re: [PATCH] softmmu/physmem: Improve guest memory allocation failure error message, Dr. David Alan Gilbert, 2021/08/24
- Re: [PATCH] softmmu/physmem: Improve guest memory allocation failure error message, David Hildenbrand, 2021/08/24
- Re: [PATCH] softmmu/physmem: Improve guest memory allocation failure error message, Igor Mammedov, 2021/08/24
Re: [PATCH] softmmu/physmem: Improve guest memory allocation failure error message, Peter Xu, 2021/08/20
Re: [PATCH] softmmu/physmem: Improve guest memory allocation failure error message, Bin Meng, 2021/08/21