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From: Andrew Cooper <andrew.cooper3@citrix.com>
To: Olaf Hering <olaf@aepfle.de>, <xen-devel@lists.xenproject.org>
Cc: George Dunlap <george.dunlap@citrix.com>,
	Ian Jackson <iwj@xenproject.org>, Jan Beulich <jbeulich@suse.com>,
	Julien Grall <julien@xen.org>,
	Stefano Stabellini <sstabellini@kernel.org>, Wei Liu <wl@xen.org>,
	Anthony PERARD <anthony.perard@citrix.com>
Subject: Re: [PATCH v4] tools: create libxensaverestore
Date: Thu, 22 Apr 2021 12:49:14 +0100	[thread overview]
Message-ID: <39eb928b-161d-4870-93d2-8c15929aa32f@citrix.com> (raw)
In-Reply-To: <20210415131138.8709-1-olaf@aepfle.de>

On 15/04/2021 14:11, Olaf Hering wrote:
> Move all save/restore related code from libxenguest.so into a separate
> library libxensaverestore.so. The only consumer is libxl-save-helper.

"in tree consumer".

It's not the only consumer, but XenServer's equivalent of
libxl-save-helper is in a position to consume this library.

That said, if you've dropped the plans for the static version, I don't
see what the point is.  You're literally saving 15 pages of memory (so
nothing in the grand scheme of a userspace process), at the cost of
added effort for the dynamic loader.

In this form, there's a reasonable chance that it adds to the perf
problems you're trying to address.

> There is no need to have the moved code mapped all the time in binaries
> where libxenguest.so is used.
> According to size(1) the change is:
>    text	   data	    bss	    dec	    hex	filename
>  187183	   4304	     48	 191535	  2ec2f	guest/libxenguest.so.4.15.0
>  124106	   3376	     48	 127530	  1f22a	guest/libxenguest.so.4.15.0
>   67841	   1872	      8	  69721	  11059	saverestore/libxensaverestore.so.4.15.0
> While touching the files anyway, take the opportunity to drop the
> reduntant xg_sr_ filename prefix.
> Signed-off-by: Olaf Hering <olaf@aepfle.de>
> ---
> diff --git a/tools/libs/saverestore/Makefile b/tools/libs/saverestore/Makefile
> new file mode 100644
> index 0000000000..48728b3be2
> --- /dev/null
> +++ b/tools/libs/saverestore/Makefile
> @@ -0,0 +1,38 @@
> +XEN_ROOT = $(CURDIR)/../../..
> +include $(XEN_ROOT)/tools/Rules.mk
> +
> +ifeq ($(CONFIG_MIGRATE),y)
> +SRCS-y += common.c
> +SRCS-$(CONFIG_X86) += common_x86.c
> +SRCS-$(CONFIG_X86) += common_x86_pv.c
> +SRCS-$(CONFIG_X86) += restore_x86_pv.c
> +SRCS-$(CONFIG_X86) += restore_x86_hvm.c
> +SRCS-$(CONFIG_X86) += save_x86_pv.c
> +SRCS-$(CONFIG_X86) += save_x86_hvm.c
> +SRCS-y += restore.c
> +SRCS-y += save.c
> +else
> +SRCS-y += nomigrate.c
> +endif

Depending on the answers to the general question above...

I don't think pulling nomigrate into this new library is sensible.  A
dedicate migration library, stubbed to errors based on some exterior
setting, is very rude.

Given the proposed new structure, the way this ought to be expressed is
libxl-save-restore-helper being conditional on CONFIG_MIGRATE in the
first place.

Also, xensaverestore is a mouthful.  If we are changing things, how
about xenmigrate instead?


  parent reply	other threads:[~2021-04-22 11:49 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-04-15 13:11 [PATCH v4] tools: create libxensaverestore Olaf Hering
2021-04-21 10:26 ` Wei Liu
2021-04-22 11:49 ` Andrew Cooper [this message]
2021-04-22 12:27   ` Olaf Hering
2021-04-22 12:46   ` Olaf Hering

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