From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id A86CCC83F11 for ; Sat, 26 Aug 2023 15:49:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231258AbjHZPtP (ORCPT ); Sat, 26 Aug 2023 11:49:15 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49184 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230317AbjHZPsq (ORCPT ); Sat, 26 Aug 2023 11:48:46 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 501C91BCD for ; Sat, 26 Aug 2023 08:48:42 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id D910761480 for ; Sat, 26 Aug 2023 15:48:41 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2C558C433C8; Sat, 26 Aug 2023 15:48:40 +0000 (UTC) Authentication-Results: smtp.kernel.org; dkim=pass (1024-bit key) header.d=zx2c4.com header.i=@zx2c4.com header.b="KpHpU7LL" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=zx2c4.com; s=20210105; t=1693064917; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=OZ8Ie87RIFTn6WUDoZfAiyIGzThKEyDxGHtS6DLKwg0=; b=KpHpU7LL7YQhBJSGctzk+yOeLMow33RuVgs1WFsTAfyK79WEiPKlJJedZV9AWN7R4ApWlQ HB+E1LgjmEpxEnSHbayUjgkkiDDAYJS0BwMhwy5otNxqfdSQPD+PV+yqF5DqH3HsLViL5V /JqMDKWZ6lUrnem+YdlPKajO1txUAws= Received: by mail.zx2c4.com (ZX2C4 Mail Server) with ESMTPSA id c17e7942 (TLSv1.3:TLS_AES_256_GCM_SHA384:256:NO); Sat, 26 Aug 2023 15:48:36 +0000 (UTC) Date: Sat, 26 Aug 2023 17:48:34 +0200 From: "Jason A. Donenfeld" To: Stefan Wahren Cc: Olivia Mackall , Herbert Xu , Florian Fainelli , Ray Jui , Scott Branden , Mark Brown , linux-crypto@vger.kernel.org, linux-arm-kernel@lists.infradead.org, bcm-kernel-feedback-list@broadcom.com Subject: Re: [PATCH] hwrng: bcm2835: Fix hwrng throughput regression Message-ID: References: <20230826112828.58046-1-wahrenst@gmx.net> <56b5000c-89d9-865e-035c-5baf730a5304@gmx.net> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <56b5000c-89d9-865e-035c-5baf730a5304@gmx.net> Precedence: bulk List-ID: X-Mailing-List: linux-crypto@vger.kernel.org On Sat, Aug 26, 2023 at 04:01:58PM +0200, Stefan Wahren wrote: > Hi Jason, > > Am 26.08.23 um 14:34 schrieb Jason A. Donenfeld: > > On Sat, Aug 26, 2023 at 01:28:28PM +0200, Stefan Wahren wrote: > >> The recent RCU stall fix caused a massive throughput regression of the > >> hwrng on Raspberry Pi 0 - 3. So try to restore a similiar throughput > >> as before the RCU stall fix. > >> > >> Some performance measurements on Raspberry Pi 3B+ (arm64/defconfig): > >> > >> sudo dd if=/dev/hwrng of=/dev/null count=1 bs=10000 > >> > >> cpu_relax ~138025 Bytes / sec > >> hwrng_msleep(1000) ~13 Bytes / sec > >> usleep_range(100,200) ~92141 Bytes / sec > >> > >> Fixes: 96cb9d055445 ("hwrng: bcm2835 - use hwrng_msleep() instead of cpu_relax()") > >> Link: https://lore.kernel.org/linux-arm-kernel/bc97ece5-44a3-4c4e-77da-2db3eb66b128@gmx.net/ > >> Signed-off-by: Stefan Wahren > >> --- > >> drivers/char/hw_random/bcm2835-rng.c | 3 ++- > >> 1 file changed, 2 insertions(+), 1 deletion(-) > >> > >> diff --git a/drivers/char/hw_random/bcm2835-rng.c b/drivers/char/hw_random/bcm2835-rng.c > >> index e98fcac578d6..3f1b6aaa98ee 100644 > >> --- a/drivers/char/hw_random/bcm2835-rng.c > >> +++ b/drivers/char/hw_random/bcm2835-rng.c > >> @@ -14,6 +14,7 @@ > >> #include > >> #include > >> #include > >> +#include > >> > >> #define RNG_CTRL 0x0 > >> #define RNG_STATUS 0x4 > >> @@ -71,7 +72,7 @@ static int bcm2835_rng_read(struct hwrng *rng, void *buf, size_t max, > >> while ((rng_readl(priv, RNG_STATUS) >> 24) == 0) { > >> if (!wait) > >> return 0; > >> - hwrng_msleep(rng, 1000); > >> + usleep_range(100, 200); > > > > I think we still need to use the hwrng_msleep function so that the sleep > > remains cancelable. Maybe just change the 1000 to 100? > i found that other hwrng driver like iproc-rng200 (Raspberry Pi 4) also > use usleep_range(). > > Nevertheless here are more numbers: > > usleep_range(200,400) : 47776 bytes / sec > hwrng_msleep(20) : 715 bytes / sec > > Changing to 100 ms won't be a real gain. I'm fine with whatever number you want there. Maybe we need a hwrng_usleep_range() that takes into account rng->dying like hwrng_msleep() does? (And iproc-rng200 should probably use that too?) Jason