From: Simon Horman <horms@verge.net.au>
To: Michael Holzheu <holzheu@linux.vnet.ibm.com>
Cc: stefan.roscher@de.ibm.com, kexec@lists.infradead.org,
Dave Young <dyoung@redhat.com>
Subject: Re: [PATCH v3] kexec/s390x: use mmap instead of read for slurp_file()
Date: Mon, 9 Nov 2015 10:59:15 +0900 [thread overview]
Message-ID: <20151109015915.GA7407@verge.net.au> (raw)
In-Reply-To: <20151030160204.6cf76607@holzheu>
On Fri, Oct 30, 2015 at 04:02:04PM +0100, Michael Holzheu wrote:
> The slurp_fd() function allocates memory and uses the read() system call.
> This results in double memory consumption for image and initrd:
>
> 1) Memory allocated in user space by the kexec tool
> 2) Memory allocated in kernel by the kexec() system call
>
> The following illustrates the use case that we have on s390x:
>
> 1) Boot a 4 GB Linux system
> 2) Copy kernel and 1,5 GB ramdisk from external source into tmpfs (ram)
> 3) Use kexec to boot kernel with ramdisk
>
> Therefore for kexec runtime we need:
>
> 1,5 GB (tmpfs) + 1,5 GB (kexec malloc) + 1,5 GB (kernel memory) = 4,5 GB
>
> This patch introduces slurp_file_mmap() which for "normal" files uses
> mmap() instead of malloc()/read(). This reduces the runtime memory
> consumption of the kexec tool as follows:
>
> 1,5 GB (tmpfs) + 1,5 GB (kernel memory) = 3 GB
>
> Signed-off-by: Michael Holzheu <holzheu@linux.vnet.ibm.com>
> Reviewed-by: Dave Young <dyoung@redhat.com>
Thanks, applied.
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next prev parent reply other threads:[~2015-11-09 1:59 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-10-23 3:10 [PATCH] Revert "kexec: use mmap instead of read for slurp_file()" Dave Young
2015-10-23 15:09 ` Michael Holzheu
2015-10-26 7:31 ` Dave Young
2015-10-27 12:35 ` [PATCH v2] kexec/s390x: use mmap instead of read for slurp_file() Michael Holzheu
2015-10-28 6:46 ` Dave Young
2015-10-28 9:57 ` Michael Holzheu
2015-10-29 6:37 ` Dave Young
2015-10-29 15:26 ` Michael Holzheu
2015-10-30 2:03 ` Dave Young
2015-10-30 10:13 ` Michael Holzheu
2015-10-30 13:39 ` Dave Young
2015-10-30 15:02 ` [PATCH v3] " Michael Holzheu
2015-11-09 1:59 ` Simon Horman [this message]
2015-10-26 4:30 ` [PATCH] Revert "kexec: use mmap instead of read for slurp_file()" Simon Horman
2015-11-03 0:11 ` Geoff Levand
2015-11-03 1:15 ` Dave Young
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