Re: [PATCH v4 2/7] migration/multifd: Implement zero page transmission on the multifd thread.

[hao . xiang]

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> On Mon, Mar 4, 2024 at 10:24 AM Fabiano Rosas <farosas@suse.de> wrote:
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>  Fabiano Rosas <farosas@suse.de> writes:
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>  Peter Xu <peterx@redhat.com> writes:
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>  On Fri, Mar 01, 2024 at 02:28:24AM +0000, Hao Xiang wrote:
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>  -GlobalProperty hw_compat_8_2[] = {};
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>  +GlobalProperty hw_compat_8_2[] = {
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>  + { "migration", "zero-page-detection", "legacy"},
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>  +};
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>  I hope we can make it for 9.0, then this (and many rest places) can be kept
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>  as-is. Let's see.. soft-freeze is March 12th.
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>  One thing to mention is I just sent a pull which has mapped-ram feature
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>  merged. You may need a rebase onto that, and hopefully mapped-ram can also
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>  use your feature too within the same patch when you repost.
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>  The key points are:
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>  - The socket migration is under "use_packets", the mapped-ram is under
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>  "!use_packets" always.
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>  - mapped-ram doesn't trasmit zero-pages, it just clears the
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>  corresponding bit in block->file_bmap.
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>  https://lore.kernel.org/all/20240229153017.2221-1-farosas@suse.de/
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>  That rebase may or may not need much caution, I apologize for that:
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>  mapped-ram as a feature was discussed 1+ years, so it was a plan to merge
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>  it (actually still partly of it) into QEMU 9.0.
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>  I started doing that rebase last week and saw issues with a sender
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>  thread always getting -EPIPE at the sendmsg() on the regular socket
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>  migration. Let's hope it was just me being tired.
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>  I'll try to get something ready this week.
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>  @Hao Xiang:
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>  Here's a branch with the rebase. Please include the first two commits
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>  when you repost:
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>  migration/multifd: Allow clearing of the file_bmap from multifd
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>  migration/multifd: Allow zero pages in file migration
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>  There are also two small additions and some conflict resolution at the
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>  "Implement zero page..." commit. Make sure you don't miss them.
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>  https://gitlab.com/farosas/qemu/-/commits/migration-multifd-zero-page
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>  Let me know if you encounter any issues.
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Sorry about the delay. I have rebased and pulled in the two commits you 
mentioned. Test works fine. I just sent out a new version.

I removed the zero/zero-bytes interface changes out of this patchset but will 
follow up with a separate one.