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Tue, 25 Feb 2025 12:05:08 -0800 (PST) Date: Tue, 25 Feb 2025 12:05:04 -0800 From: Kevin Krakauer To: Jakub Kicinski Cc: davem@davemloft.net, edumazet@google.com, horms@kernel.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, netdev@vger.kernel.org, pabeni@redhat.com, shuah@kernel.org Subject: Re: [PATCH] selftests/net: deflake GRO tests and fix return value and output Message-ID: References: <20250220170409.42cce424@kernel.org> <20250223151949.1886080-1-krakauer@google.com> <20250224124830.7c38608a@kernel.org> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250224124830.7c38608a@kernel.org> On Mon, Feb 24, 2025 at 12:48:30PM -0800, Jakub Kicinski wrote: > With msec-long deferrals we'll flush due to jiffies change. At least > that explains a bit. Could you maybe try lower timeouts than 1msec? > Previously we'd just keep partially-completed packets in GRO for up > to 1msec, now we'll delay all packet processing for 1msec, that's a lot. Results again with each test run 1000 times: gro_flush_timeout=50us napi_defer_hard_irqs=1 --> failed to GRO 0 times gro_flush_timeout=100us napi_defer_hard_irqs=1 --> failed to GRO 0 times gro_flush_timeout=50us napi_defer_hard_irqs=0 --> failed to GRO 36 times gro_flush_timeout=100us napi_defer_hard_irqs=0 --> failed to GRO 46 times 100us with 1 defer seems to work fine and is well below the duration of a jiffy. So we'll usually be testing the "default" GRO path and only occasionally the jiffy-update path. I'll make these the numbers in the revised patch unless someone thinks otherwise.