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[46.139.12.213]) by smtp.gmail.com with ESMTPSA id t5sm9130743wmg.43.2019.02.11.04.51.48 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Mon, 11 Feb 2019 04:51:48 -0800 (PST) Date: Mon, 11 Feb 2019 13:51:46 +0100 From: Ingo Molnar To: Mark Brown Cc: Shuah Khan , Thomas Gleixner , Ingo Molnar , Borislav Petkov , "H . Peter Anvin" , Andy Lutomirski , linux-kernel@vger.kernel.org, x86@kernel.org, linux-kselftest@vger.kernel.org, Dan Rue Subject: Re: [PATCH 2/2] selftests/x86/fsgsbase: Default to trying to run the test repeatedly Message-ID: <20190211125146.GA66987@gmail.com> References: <20190203134017.9375-1-broonie@kernel.org> <20190203134017.9375-3-broonie@kernel.org> <20190211084916.GB62722@gmail.com> <20190211124738.GA22391@sirena.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190211124738.GA22391@sirena.org.uk> User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Mark Brown wrote: > On Mon, Feb 11, 2019 at 09:49:16AM +0100, Ingo Molnar wrote: > > > So this isn't very user-friendly either, previously it would run a > > testcase and immediately provide output. > > > Now it's just starting and 'hanging': > > > galatea:~/linux/linux/tools/testing/selftests/x86> ./fsgsbase_64 > > > I got bored and Ctrl-C-ed it after ~30 seconds. > > > How long is this supposed to run, and why isn't the user informed? > > On Intel systems I've got access to it's tended to only run for less > than 10 seconds for me with excursions up to ~30s at most, I'd have > projected it to be about a minute if the tests pass. However retesting > with Debian's v4.19 kernel it seems to be running a lot more stably so > we're now seeing it run to completion reliably when just one copy of the > test is running. > > AFAICT it's not terribly idiomatic to provide much output, and anything > that was per iteration would be *way* too spammy. Certainly - but a "please wait" and updating the current count via \r once every second isn't spammy. > > Also, testcases should really be short, so I think a better approach > > would be to thread the test-case and start an instance on every CPU. That > > should also excercise SMP bugs, if any. > > Well, a *better* approach would be for the underlying issue that the > test is finding to be fixed. > > I didn't look at adding more threads as the test case is already > threaded, it does seem that running multiple copies simultaneously makes > things reproduce more quickly so it's definitely useful though it's > still taking multiple iterations. multiple iterations are fine - waiting a minute with zero output on the console isn't. Thanks, Ingo From mboxrd@z Thu Jan 1 00:00:00 1970 From: mingo at kernel.org (Ingo Molnar) Date: Mon, 11 Feb 2019 13:51:46 +0100 Subject: [PATCH 2/2] selftests/x86/fsgsbase: Default to trying to run the test repeatedly In-Reply-To: <20190211124738.GA22391@sirena.org.uk> References: <20190203134017.9375-1-broonie@kernel.org> <20190203134017.9375-3-broonie@kernel.org> <20190211084916.GB62722@gmail.com> <20190211124738.GA22391@sirena.org.uk> Message-ID: <20190211125146.GA66987@gmail.com> * Mark Brown wrote: > On Mon, Feb 11, 2019 at 09:49:16AM +0100, Ingo Molnar wrote: > > > So this isn't very user-friendly either, previously it would run a > > testcase and immediately provide output. > > > Now it's just starting and 'hanging': > > > galatea:~/linux/linux/tools/testing/selftests/x86> ./fsgsbase_64 > > > I got bored and Ctrl-C-ed it after ~30 seconds. > > > How long is this supposed to run, and why isn't the user informed? > > On Intel systems I've got access to it's tended to only run for less > than 10 seconds for me with excursions up to ~30s at most, I'd have > projected it to be about a minute if the tests pass. However retesting > with Debian's v4.19 kernel it seems to be running a lot more stably so > we're now seeing it run to completion reliably when just one copy of the > test is running. > > AFAICT it's not terribly idiomatic to provide much output, and anything > that was per iteration would be *way* too spammy. Certainly - but a "please wait" and updating the current count via \r once every second isn't spammy. > > Also, testcases should really be short, so I think a better approach > > would be to thread the test-case and start an instance on every CPU. That > > should also excercise SMP bugs, if any. > > Well, a *better* approach would be for the underlying issue that the > test is finding to be fixed. > > I didn't look at adding more threads as the test case is already > threaded, it does seem that running multiple copies simultaneously makes > things reproduce more quickly so it's definitely useful though it's > still taking multiple iterations. multiple iterations are fine - waiting a minute with zero output on the console isn't. Thanks, Ingo From mboxrd@z Thu Jan 1 00:00:00 1970 From: mingo@kernel.org (Ingo Molnar) Date: Mon, 11 Feb 2019 13:51:46 +0100 Subject: [PATCH 2/2] selftests/x86/fsgsbase: Default to trying to run the test repeatedly In-Reply-To: <20190211124738.GA22391@sirena.org.uk> References: <20190203134017.9375-1-broonie@kernel.org> <20190203134017.9375-3-broonie@kernel.org> <20190211084916.GB62722@gmail.com> <20190211124738.GA22391@sirena.org.uk> Message-ID: <20190211125146.GA66987@gmail.com> Content-Type: text/plain; charset="UTF-8" Message-ID: <20190211125146.fa1T7mIdFjHZBYxx8t3H1q54bWigm55aAXwhJyUsWG4@z> * Mark Brown wrote: > On Mon, Feb 11, 2019@09:49:16AM +0100, Ingo Molnar wrote: > > > So this isn't very user-friendly either, previously it would run a > > testcase and immediately provide output. > > > Now it's just starting and 'hanging': > > > galatea:~/linux/linux/tools/testing/selftests/x86> ./fsgsbase_64 > > > I got bored and Ctrl-C-ed it after ~30 seconds. > > > How long is this supposed to run, and why isn't the user informed? > > On Intel systems I've got access to it's tended to only run for less > than 10 seconds for me with excursions up to ~30s at most, I'd have > projected it to be about a minute if the tests pass. However retesting > with Debian's v4.19 kernel it seems to be running a lot more stably so > we're now seeing it run to completion reliably when just one copy of the > test is running. > > AFAICT it's not terribly idiomatic to provide much output, and anything > that was per iteration would be *way* too spammy. Certainly - but a "please wait" and updating the current count via \r once every second isn't spammy. > > Also, testcases should really be short, so I think a better approach > > would be to thread the test-case and start an instance on every CPU. That > > should also excercise SMP bugs, if any. > > Well, a *better* approach would be for the underlying issue that the > test is finding to be fixed. > > I didn't look at adding more threads as the test case is already > threaded, it does seem that running multiple copies simultaneously makes > things reproduce more quickly so it's definitely useful though it's > still taking multiple iterations. multiple iterations are fine - waiting a minute with zero output on the console isn't. Thanks, Ingo