From: Helmut Schaa Subject: Re: [PATCH] crypto: talitos: Avoid excessive loops in softirq context Date: Mon, 15 Sep 2014 10:40:38 +0200 Message-ID: References: <1410338087-5317-1-git-send-email-helmut.schaa@googlemail.com> <20140911194918.9ea4795f7bb3f9d6e32490eb@freescale.com> <20140912182126.2d913df25f491416c3a1a677@freescale.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Cc: linux-crypto@vger.kernel.org, Herbert Xu , David Miller , Sandeep Malik , Horia Geanta , netdev To: Kim Phillips Return-path: In-Reply-To: <20140912182126.2d913df25f491416c3a1a677@freescale.com> Sender: netdev-owner@vger.kernel.org List-Id: linux-crypto.vger.kernel.org On Sat, Sep 13, 2014 at 1:21 AM, Kim Phillips wrote: > [adding Sandeep, Horia and netdev] > > On Fri, 12 Sep 2014 09:39:12 +0200 > Helmut Schaa wrote: > >> On Fri, Sep 12, 2014 at 2:49 AM, Kim Phillips >> wrote: >> > On Wed, 10 Sep 2014 10:34:47 +0200 >> > Helmut Schaa wrote: >> > >> >> The talitos driver can cause starvation of other softirqs and as such >> >> it can also cause rcu stalls like: >> > ... >> >> Work around this by processing a maximum amount of 16 finished requests >> >> and rescheduling the done-tasklet if any work is left. >> >> This allows other softirqs to run. >> > >> > 16 sounds rather arbitrary, and application-dependent - talitos' >> > FIFO size is 24. >> >> Yep, 16 is arbitrary, I can also do "fifo_len" if you prefer? >> >> > IIRC, netdev's NAPI can be refactored out of just being able to work >> > on network devices, and be made to apply to crypto devices, too. In >> > fact, some old Freescale hacks of this nature have improved >> > performance. Can we do something like refactor NAPI instead? >> >> That would indeed be nice but sounds like quite some more work and >> I won't have time to do so. Especially since my system was taken down >> completely by the talitos tasklet under some circumstances. If there is >> any work going on in that regard I'd be fine with just dropping that patch >> (and carrying it myself until the refactoring is done). > > I'm not aware of any, but to prove whether NAPI actually fixes the > issue, can you try applying this patch: > http://patchwork.ozlabs.org/patch/146094/ I guess this would fix it too. Will run some tests soon. Helmut