Re: [Xen-devel] Slow HVM boot time, was "HVM boot time optimization"

[Yessine Daoud <da.yessine@xxxxxxxxx>]

Hello,

I tried to debug the issue and this what I found:

the HVM boot takes some time at the following section (qemu/pc-bios/optionrom/linuxboot.S)

/* Load kernel and initrd */

read_fw_blob_addr32_edi(FW_CFG_INITRD) (ramdisk about 3M takes ~~7.s)

read_fw_blob_addr32(FW_CFG_KERNEL) (vmlinuz about 7M takes ~~15.s)

read_fw_blob_addr32(FW_CFG_CMDLINE)

#define read_fw_blob_addr32(var) \

read_fw var ## _ADDR; \

mov %eax, %edi; \

read_fw_blob_pre(var); \

/* old as(1) doesn't like this insn so emit the bytes instead: \

addr32 rep insb (%dx), %es:(%edi); \

*/ \

.dc.b 0x67,0xf3,0x6c

#define read_fw_blob_addr32_edi(var) \

read_fw_blob_pre(var); \

/* old as(1) doesn't like this insn so emit the bytes instead: \

addr32 rep insb (%dx), %es:(%edi); \

*/ \

.dc.b 0x67,0xf3,0x6c

Any idea how to speed the  I/O read ?

Thanks.

ᐧ

2018-02-12 15:42 GMT+01:00 Wei Liu <wei.liu2@xxxxxxxxxx>:

On Mon, Feb 12, 2018 at 09:27:25AM +0100, Yessine Daoud wrote:
>  Hello,
>
> Thank you for your quick response.
> Any hints how can I "fix" this "issue"? *Any workaround?
>

Honestly I have no idea why it is slow unless there is more logging
available.

Wei.

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