[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [Qemu-block] [PATCH v3] migration/block:limit the time used for bloc
From: |
Stefan Hajnoczi |
Subject: |
Re: [Qemu-block] [PATCH v3] migration/block:limit the time used for block migration |
Date: |
Thu, 6 Apr 2017 15:02:55 +0100 |
User-agent: |
Mutt/1.8.0 (2017-02-23) |
On Wed, Apr 05, 2017 at 05:27:58PM +0800, address@hidden wrote:
> From: Lidong Chen <address@hidden>
>
> when migration with high speed, mig_save_device_bulk invoke
> bdrv_is_allocated too frequently, and cause vnc reponse slowly.
> this patch limit the time used for bdrv_is_allocated.
bdrv_is_allocated() is supposed to yield back to the event loop if it
needs to block. If your VNC session is experiencing jitter then it's
probably because a system call in the bdrv_is_allocated() code path is
synchronous when it should be asynchronous.
You could try to identify the system call using strace -f -T. In the
output you'll see the duration of each system call. I guess there is a
file I/O system call that is taking noticable amounts of time.
A proper solution is to refactor the synchronous code to make it
asynchronous. This might require invoking the system call from a
thread pool worker.
Stefan
signature.asc
Description: PGP signature
- [Qemu-block] [PATCH v3] migration/block:limit the time used for block migration, jemmy858585, 2017/04/05
- Re: [Qemu-block] [Qemu-devel] [PATCH v3] migration/block:limit the time used for block migration, Daniel P. Berrange, 2017/04/05
- Re: [Qemu-block] [PATCH v3] migration/block:limit the time used for block migration,
Stefan Hajnoczi <=
- Re: [Qemu-block] [PATCH v3] migration/block:limit the time used for block migration, Stefan Hajnoczi, 2017/04/07
- Re: [Qemu-block] [PATCH v3] migration/block:limit the time used for block migration, 858585 jemmy, 2017/04/08
- Re: [Qemu-block] [PATCH v3] migration/block:limit the time used for block migration, Stefan Hajnoczi, 2017/04/10
- Re: [Qemu-block] [PATCH v3] migration/block:limit the time used for block migration, 858585 jemmy, 2017/04/11