From: Grygorii Strashko Subject: Re: [PATCH 02/28] crypto: omap-sham: Don't idle/start SHA device between Encrypt operations Date: Tue, 7 Jun 2016 15:24:43 +0300 Message-ID: <5756BD0B.4030506@ti.com> References: <1464771389-10640-1-git-send-email-t-kristo@ti.com> <1464771389-10640-3-git-send-email-t-kristo@ti.com> <574EB091.6040001@ti.com> <574F69D8.1010809@ti.com> <20160607100837.GA30875@gondor.apana.org.au> <5756B584.2000900@ti.com> Mime-Version: 1.0 Content-Type: text/plain; charset="windows-1252"; format=flowed Content-Transfer-Encoding: 7bit Cc: , , , , , To: Tero Kristo , Herbert Xu , Dave Gerlach Return-path: Received: from comal.ext.ti.com ([198.47.26.152]:38353 "EHLO comal.ext.ti.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754756AbcFGMZQ (ORCPT ); Tue, 7 Jun 2016 08:25:16 -0400 In-Reply-To: <5756B584.2000900@ti.com> Sender: linux-crypto-owner@vger.kernel.org List-ID: On 06/07/2016 02:52 PM, Tero Kristo wrote: > On 07/06/16 13:08, Herbert Xu wrote: >> On Wed, Jun 01, 2016 at 06:03:52PM -0500, Dave Gerlach wrote: >>> On 06/01/2016 04:53 AM, Grygorii Strashko wrote: >>>> On 06/01/2016 11:56 AM, Tero Kristo wrote: >>>>> From: Lokesh Vutla >>>>> >>>>> Calling runtime PM API for every block causes serious perf hit to >>>>> crypto operations that are done on a long buffer. >>>>> As crypto is performed on a page boundary, encrypting large buffers >>>>> can >>>>> cause a series of crypto operations divided by page. The runtime PM >>>>> API >>>>> is also called those many times. >>>>> >>>>> We call runtime_pm_get_sync only at beginning on the session >>>>> (cra_init) >>>>> and runtime_pm_put at the end. This result in upto a 50% speedup. >>>>> This doesn't make the driver to keep the system awake as runtime >>>>> get/put >>>>> is only called during a crypto session which completes usually >>>>> quickly. >>>>> >>>>> Signed-off-by: Lokesh Vutla >>>>> Signed-off-by: Tero Kristo >>>>> --- >>>>> drivers/crypto/omap-sham.c | 27 +++++++++++++++++---------- >>>>> 1 file changed, 17 insertions(+), 10 deletions(-) >>>>> >>>>> diff --git a/drivers/crypto/omap-sham.c b/drivers/crypto/omap-sham.c >>>>> index 6eefaa2..bd0258f 100644 >>>>> --- a/drivers/crypto/omap-sham.c >>>>> +++ b/drivers/crypto/omap-sham.c >>>>> @@ -360,14 +360,6 @@ static void omap_sham_copy_ready_hash(struct >>>>> ahash_request *req) >>>>> >>>>> static int omap_sham_hw_init(struct omap_sham_dev *dd) >>>>> { >>>>> - int err; >>>>> - >>>>> - err = pm_runtime_get_sync(dd->dev); >>>>> - if (err < 0) { >>>>> - dev_err(dd->dev, "failed to get sync: %d\n", err); >>>>> - return err; >>>>> - } >>>>> - >>> >>> Would it be worth it to investigate a pm_runtime autosuspend >>> approach rather than knocking runtime PM out here completely? I am >>> not clear if the overhead is coming from the pm_runtime calls >>> themselves or the actual idling of the IP, but if it's the idling of >>> the IP causing the slowdown, with a large enough autosuspend_delay >>> we don't actually sleep between each block but after a long enough >>> period of idle time we would actually suspend. >> >> Indeed, I think this patch is bogus. cra_init is associated >> with the tfm object which is usually long-lived. So doing power >> management there makes no sense. >> >> Cheers, >> > > I can investigate this further, but I believe this patch itself gave a > noticeable performance boost. > > This is an optimization anyway, and not critical for functionality. > It is not critical only if below code would not introduce races + spin_lock_bh(&sham.lock); + list_for_each_entry(dd, &sham.dev_list, list) { + break; + } + spin_unlock_bh(&sham.lock); Is it guaranteed that dd will alive always at this moment? + + pm_runtime_get_sync(dd->dev); -- regards, -grygorii