Ksmbd and max credits

Ksmbd and max credits

[Steve French]

Thinking about the patch "ksmbd: improve credits management"
(https://github.com/smfrench/smb3-kernel/commit/bf8acc9e10e21c28452dfa067a7d31e6067104b1)

Hyunchul noted in the description:
"Windows server 2016 or later grant up to 8192 credits to clients at once."

I noticed that SMB2_MAX_CREDITS is defined as 8192 in
fs/ksmbd/smb2pdu.h.  Isn't this a little low, although I see Samba
default to it as well.

Was thinking that that is roughly equivalent to 64 8MB writes, or 128
4MB writes.   Although Samba defaults to 8192 max credits as well, for
Samba it is configurable (via "smb2 max credits" in smb.conf).
Should it be configurable?  What do more current Windows servers
default to as the max?


-- 
Thanks,

Steve

Re: Ksmbd and max credits

[Hyunchul Lee]

2021년 10월 14일 (목) 오후 2:03, Steve French <smfrench@gmail.com>님이 작성:
>
> Thinking about the patch "ksmbd: improve credits management"
> (https://github.com/smfrench/smb3-kernel/commit/bf8acc9e10e21c28452dfa067a7d31e6067104b1)
>
> Hyunchul noted in the description:
> "Windows server 2016 or later grant up to 8192 credits to clients at once."
>
> I noticed that SMB2_MAX_CREDITS is defined as 8192 in
> fs/ksmbd/smb2pdu.h.  Isn't this a little low, although I see Samba
> default to it as well.
>
> Was thinking that that is roughly equivalent to 64 8MB writes, or 128
> 4MB writes.   Although Samba defaults to 8192 max credits as well, for
> Samba it is configurable (via "smb2 max credits" in smb.conf).
> Should it be configurable?  What do more current Windows servers
> default to as the max?
>

According to MS-SMB2, the maximum credit limit is configurable, but
the default maximum credit limit in Windows Server 2022 is also 8192.

It looks good if it can be configurable, but I can't find out the possible range
of values.
And there is a description, "You should never need to set this parameter"
about "smb2 max credits in smb.conf" in the Samba manual.

>
> --
> Thanks,
>
> Steve



-- 
Thanks,
Hyunchul