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From: | Denis Plotnikov |
Subject: | Re: [PATCH v1 2/4] virtio: increase virtuqueue size for virtio-scsi and virtio-blk |
Date: | Thu, 9 Sep 2021 14:26:29 +0300 |
User-agent: | Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.13.0 |
On 09.09.2021 11:28, Stefano Garzarella wrote:
On Wed, Sep 08, 2021 at 06:20:49PM +0300, Denis Plotnikov wrote:On 08.09.2021 16:22, Stefano Garzarella wrote:Message bounced, I use new Denis's email address. On Wed, Sep 08, 2021 at 03:17:16PM +0200, Stefano Garzarella wrote:Hi Denis,I just found this discussion since we still have the following line in hw/core/machine.c:{ "vhost-blk-device", "seg_max_adjust", "off"}IIUC it was a typo, and I think we should fix it since in the future we can have `vhost-blk-device`.So, I think we have 2 options: 1. remove that line since for now is useless 2. replace with "vhost-scsi" I'm not sure which is the best, what do you suggest? Thanks, StefanoHi StefanoI prefer to just remove the line without replacing. This will keep things exactly like it is now.Replacing with "vhost-scsi" will affect seg_max (limit to 126) on newly created VMs with machine types using "hw_compat_4_2" and older.Now, because of the typo (error), their seg-max is queue-size dependent. I'm not sure, if replacing the line may cause any problems, for example on migration: source (queue-size 256, seg max 254) -> destination (queue-size 256, seg max 126). But it will definitely introduce two different behaviors for VMs with "hw_compat_4_2" and older. So, I'd choose the lesser of two evils and keep the things like it's now.Yep, make sense. It was the same concern I had. Do you want to send a patch to remove it with this explanation?
Yes, sure. I'll do it today. Denis
Thanks for the clarification, Stefano
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