linux-kernel - Re: [PATCH 1/2] include: trace: Add SCMI header with trace events

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <9befbc13-ba00-094d-0064-0d97c1ccbb63@broadcom.com>
Date:   Fri, 20 Dec 2019 11:24:03 -0500
From:   Jim Quinlan <james.quinlan@...adcom.com>
To:     Lukasz Luba <lukasz.luba@....com>,
        Sudeep Holla <sudeep.holla@....com>
Cc:     linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        mingo@...hat.com, rostedt@...dmis.org
Subject: Re: [PATCH 1/2] include: trace: Add SCMI header with trace events


> Thank you for sharing your experiments and thoughts. I have probably
> similar setup for stressing the communication channel, but I do also
> some wired things in the firmware. That's why I need to measure these
> delays. I am happy that it is useful for you also.
>
> I don't know if your firmware supports 'fast channel', but please keep
> in mind that it is not tracked in this 'transfer_id'.
> This transfer_id in v2 version does not show the real transfers
> to the firmware since there is another path called 'fast channel' or
> 'fast_switch' in the CPUfreq. It is in drivers/firmware/arm_scmi/perf.c
> and the atomic variable is not incremented in that path. Adding it also
> there just for atomic_inc() probably would add delays in the fast_switch
> and also brings little value.
> For the normal channel, where we have spinlocks and other stuff, this
> atomic_inc() could stay in my opinion.
>
> Regards,
> Lukasz
Hi Lukasz,

We currently do not use "fast channels" - although it is possible we might someday.
I find the transfer_id useful per your v2 even if it doesn't cover FC.  Thanks for
submitting and discussing this!

Regards,
Jim Quinlan