Guys
I forgot to create /boot partition for a centos machine and it is productive now.
Is there any impact on performance or any risk.
Is iit a must to rebuild, that will be very hard to do for many reasons (applications deployed)
thanks

Unless your root partition is encrypted or under some disk space management that GRUB does not understand, there is no advantage to having a separate /boot. And since your system boots and runs, it is obvious that none of those conditions apply.

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The only place that a separate /boot partition is significant is in older systems with BIOS that doesn't recognize large disks. In such circumstances, you can save a lot of problems by creating a /boot partition that guarantees all blocks will be below the 1024 cylinder limit. Large disks are a problem here because system updates may allocate blocks outside the limits for the kernel - which can't be loaded.

As stated, an encrypted root partition will cause problems because the kernel itself will be encrypted... and grub can't/won't be able to decrypt it.

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There are lots of ways to have a / partition that the first stage of grub can't read (various LVM or RAID configurations, etc.).

Very likely the majority of Centos systems have / partitions that grub can't access and thus they need /boot partitions.

Obviously grub can access your / partition. There is no performance nor risk issue there. It is a binary thing: works or doesn't work. Your /boot directory works, so you don't have any reason to "fix" it.

In the early days of Linux (before liveCDs) there was risk to having /boot as a directory in / rather than as a partition. But this is ancient history now.

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Thank you all guys
I am not using any LVM or encrypted root partition.
I think I can sleep without nightmares