[PATCH] Add more description for --num-threads

[Chao Fan]

Ack.

Since in the condition of "-d 31", it will cost more time with
"--num-threads" than without "--num-threads". So I suggest not
using "--num-threads" when "-d 31" will be better.

Acked-by: Chao Fan <cfan at redhat.com>

----- Original Message -----
> From: "Zhou Wenjian" <zhouwj-fnst at cn.fujitsu.com>
> To: kexec at lists.infradead.org
> Sent: Thursday, December 3, 2015 10:50:11 AM
> Subject: [PATCH] Add more description for --num-threads
> 
> From the test result, we can see when "-d 31" is specified, using
> "--num-threads" always spends more time than not. And it occurs at
> most of the time in theory. So it should be mentioned in the
> description of "--num-threads".
> 
> Signed-off-by: Zhou Wenjian <zhouwj-fnst at cn.fujitsu.com>
> ---
>  makedumpfile.8 | 6 ++++--
>  print_info.c   | 4 ++++
>  2 files changed, 8 insertions(+), 2 deletions(-)
> 
> diff --git a/makedumpfile.8 b/makedumpfile.8
> index 6eff4f1..ec179a5 100644
> --- a/makedumpfile.8
> +++ b/makedumpfile.8
> @@ -378,11 +378,13 @@ Using multiple threads to read and compress data of
> each page in parallel.
>  And it will reduces time for saving \fIDUMPFILE\fR.
>  This feature only supports creating \fIDUMPFILE\fR in kdump\-comressed
>  format from \fIVMCORE\fR in kdump\-compressed format or elf format.
> +Note that if too many pages are filtered, \'\-\-num\-threads\' may not
> improve
> +the performance, or even has bad effects. It means if \'\-d 31\' is
> specified,
> +you should think about whether to use \'\-\-num\-threads\'.
>  .br
>  .B Example:
>  .br
> -# makedumpfile \-d 31 \-\-num\-threads 4 /proc/vmcore dumpfile
> -
> +# makedumpfile \-\-num\-threads 4 /proc/vmcore dumpfile
>  .TP
>  \fB\-\-reassemble\fR
>  Reassemble multiple \fIDUMPFILE\fRs, which are created by \-\-split option,
> diff --git a/print_info.c b/print_info.c
> index d662c0c..d0302a8 100644
> --- a/print_info.c
> +++ b/print_info.c
> @@ -194,6 +194,10 @@ print_usage(void)
>  	MSG("      And it will reduces time for saving DUMPFILE.\n");
>  	MSG("      This feature only supports creating DUMPFILE in kdump-comressed
>  	format from\n");
>  	MSG("      VMCORE in kdump-compressed format or elf format.\n");
> +	MSG("      Note that if too many pages are filtered, '--num-threads' may
> not improve\n");
> +	MSG("      the performance, or even has bad effects.\n");
> +	MSG("      It means if '-d 31' is specified, you should think about whether
> to use\n");
> +	MSG("      '--num-threads'.\n");
>  	MSG("\n");
>  	MSG("  [--reassemble]:\n");
>  	MSG("      Reassemble multiple DUMPFILEs, which are created by --split
>  	option,\n");
> --
> 1.8.3.1
> 
> 
> 
> 
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