linux-kernel - Re: [RFC PATCH 0/1] dm-crypt excessive overhead

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Message-ID: <CALrw=nHZK7JhUO+-vAeMxCZqTBGBkWckBeg56pFuc1bo6yep6A@mail.gmail.com>
Date:   Sat, 20 Jun 2020 22:02:36 +0100
From:   Ignat Korchagin <ignat@...udflare.com>
To:     Mikulas Patocka <mpatocka@...hat.com>
Cc:     Herbert Xu <herbert@...dor.apana.org.au>,
        "David S. Miller" <davem@...emloft.net>,
        Mike Snitzer <snitzer@...hat.com>, agk@...hat.com,
        dm-devel@...hat.com, dm-crypt@...ut.de,
        linux-kernel <linux-kernel@...r.kernel.org>,
        kernel-team <kernel-team@...udflare.com>
Subject: Re: [RFC PATCH 0/1] dm-crypt excessive overhead

Yes, it should.

I got one when I was testing the first iteration (without the tasklet)
of the patch on an NVME? disk.

On Sat, Jun 20, 2020 at 8:36 PM Mikulas Patocka <mpatocka@...hat.com> wrote:
>
>
>
> On Sat, 20 Jun 2020, Herbert Xu wrote:
>
> > On Fri, Jun 19, 2020 at 02:39:39PM -0400, Mikulas Patocka wrote:
> > >
> > > I'm looking at this and I'd like to know why does the crypto API fail in
> > > hard-irq context and why does it work in tasklet context. What's the exact
> > > reason behind this?
> >
> > You're not supposed to do any real work in IRQ handlers.  All
> > the substantial work should be postponed to softirq context.
>
> I see.
>
> BTW - should it also warn if it is running in a process context with
> interrupts disabled?
>
> Mikulas
>
> > Why do you need to do work in hard IRQ context?
> >
> > Cheers,
> > --
> > Email: Herbert Xu <herbert@...dor.apana.org.au>
> > Home Page: http://gondor.apana.org.au/~herbert/
> > PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
> >
>