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Re: [Qemu-devel] [PATCH V7 6/6] hostmem-file: add 'sync' option
From: |
Michael S. Tsirkin |
Subject: |
Re: [Qemu-devel] [PATCH V7 6/6] hostmem-file: add 'sync' option |
Date: |
Wed, 19 Dec 2018 10:59:10 -0500 |
On Wed, Dec 19, 2018 at 05:10:18PM +0800, Yi Zhang wrote:
> > > +
> > > + - 'sync' option of memory-backend-file is not 'off', and
> > > +
> > > + - 'share' option of memory-backend-file is 'on'.
> > > +
> > > + - 'pmem' option of memory-backend-file is 'on'
> > > +
> >
> > Wait isn't this what pmem was supposed to do?
> > Doesn't it mean "persistent memory"?
> pmem is a option for memory-backend-file, user should know the backend
> is in host persistent memory, with this flags on, while there is a host crash
> or a power failures.
>
> [1] Qemu will take necessary operations to guarantee the persistence.
> https://patchwork.ozlabs.org/cover/944749/
>
> [2] Host kernel also take opretions to consistent filesystem metadata.
> Add MAP_SYNC flags.
OK so I'm a user. Can you educate me please? When should MAP_SYNC not
be set? Are there any disadvantages (e.g. performance?)?
--
MST
- Re: [Qemu-devel] [PATCH V7 2/6] util/mmap-alloc: switch qemu_ram_mmap() to 'flags' parameter, (continued)
- [Qemu-devel] [PATCH V7 4/6] util/mmap-alloc: Switch the RAM_SYNC flags to OnOffAuto, Zhang Yi, 2018/12/18
- [Qemu-devel] [PATCH V7 5/6] hostmem: add more information in error messages, Zhang Yi, 2018/12/18
- [Qemu-devel] [PATCH V7 6/6] hostmem-file: add 'sync' option, Zhang Yi, 2018/12/18
- Re: [Qemu-devel] [PATCH V7 6/6] hostmem-file: add 'sync' option, Michael S. Tsirkin, 2018/12/18
- Re: [Qemu-devel] [PATCH V7 6/6] hostmem-file: add 'sync' option, Yi Zhang, 2018/12/19
- Re: [Qemu-devel] [PATCH V7 6/6] hostmem-file: add 'sync' option,
Michael S. Tsirkin <=
- Re: [Qemu-devel] [PATCH V7 6/6] hostmem-file: add 'sync' option, Yi Zhang, 2018/12/19
- Re: [Qemu-devel] [PATCH V7 6/6] hostmem-file: add 'sync' option, Michael S. Tsirkin, 2018/12/19
- Re: [Qemu-devel] [PATCH V7 6/6] hostmem-file: add 'sync' option, Yi Zhang, 2018/12/20
- Re: [Qemu-devel] [PATCH V7 6/6] hostmem-file: add 'sync' option, Michael S. Tsirkin, 2018/12/20
- Re: [Qemu-devel] [PATCH V7 6/6] hostmem-file: add 'sync' option, Yi Zhang, 2018/12/20
- Re: [Qemu-devel] [PATCH V7 6/6] hostmem-file: add 'sync' option, Michael S. Tsirkin, 2018/12/21
- Re: [Qemu-devel] [PATCH V7 6/6] hostmem-file: add 'sync' option, Yi Zhang, 2018/12/24
Re: [Qemu-devel] [PATCH V7 0/6] nvdimm: support MAP_SYNC for memory-backend-file, Stefan Hajnoczi, 2018/12/18