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Re: [PATCH v3 00/21] Multifd Migration Compression

From: Juan Quintela
Subject: Re: [PATCH v3 00/21] Multifd Migration Compression
Date: Thu, 23 Jan 2020 13:17:47 +0100
User-agent: Gnus/5.13 (Gnus v5.13) Emacs/26.3 (gnu/linux)

Juan Quintela <address@hidden> wrote:
> [v3]
> - rebased on top of upstream + previous multifd cancel series
> - split multifd code into its own file (multifd.[ch])
> - split zstd/zlib compression methods (multifd-zstd/zlib.c)
> - use qemu module feauture to avoid ifdefs
>   (my understanding is that zlib needs to be present, but
>   we setup zstd only if it is not there or is disabled)
> - multifd-method: none|zlib|zstd
>   As far as I can see, there is no easy way to convince qapi that zstd
>   option could/couldn't be there depending on compliation flags. I
>   ended just checking in migrate_parameters_check() if it is enabled
>   and giving an error message otherwise.
> Questions:
> - I am "reusing" the compress-level parameter for both zstd and zlib,
>   but it poses a problem:
>   * zlib values: 1-9 (default: 6?)
>   * zstd values: 1-19 (default: 3)
> So, what should I do:
>   * create multifd-zstd-level and multifd-zlib-level (easier)
>   * reuse compress-level, and change its maximum values depending on
>     multifd-method
>   * any other good option?
> Please, review.
> [v2] - rebase on top of previous arguments posted to the list -
> introduces zlib compression - introduces zstd compression
> Please help if you know anything about zstd/zlib compression.
> This puts compression on top of multifd. Advantages about current
> compression:
> - We copy all pages in a single packet and then compress the whole
>   thing.
> - We reuse the compression stream for all the packets sent through the
>   same channel.
> - We can select nocomp/zlib/zstd levels of compression.
> Please, review.
> Juan Quintela (21):
>   migration-test: Use g_free() instead of free()
>   multifd: Make sure that we don't do any IO after an error
>   qemu-file: Don't do IO after shutdown
>   migration-test: Make sure that multifd and cancel works
>   migration: Create migration_is_running()
>   migration: Don't send data if we have stopped

This patches are from my previous series.  I forgot to pass the -b
option to git-publish.  Please ignore them.

Sorry, Juan.

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