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([2804:7f0:b753:c149:7884:c5c7:2b46:5945]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-73048c1623dsm1450077b3a.132.2025.02.06.07.24.43 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 06 Feb 2025 07:24:44 -0800 (PST) Message-ID: <01ce78a4-0780-4af0-a9ca-6f654934ec9e@redhat.com> Date: Thu, 6 Feb 2025 12:24:42 -0300 Precedence: bulk X-Mailing-List: linux-rt-users@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] Change min/max to float numbers To: Sebastian Andrzej Siewior Cc: williams@redhat.com, jkacur@redhat.com, linux-rt-users@vger.kernel.org References: <3a9f0f10-2e7a-4eb6-b094-e5492b43505f@redhat.com> <20250206120056.oE88fgG6@linutronix.de> <2cb9215a-61d8-4b97-af66-6ef4194f3e04@redhat.com> <20250206150947.GYesymE5@linutronix.de> Content-Language: en-US From: Rafael Folco In-Reply-To: <20250206150947.GYesymE5@linutronix.de> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 06/02/25 12:09, Sebastian Andrzej Siewior wrote: > On 2025-02-06 12:02:49 [-0300], Rafael Folco wrote: >> On 06/02/25 09:00, Sebastian Andrzej Siewior wrote: >>> On 2025-02-06 06:16:22 [-0300], Rafael Folco wrote: >>>> Make min/max consistent with avg by recording the latency samples >>>> as float numbers instead of integers. >>> >>> Why? >> >> - More precise numbers of Max/Min for extreme low latency cases >> - Distinguish zero latency in bucket 001 (us) >> - Distinguish values from upper/lower boundaries in a bucket >> - Clarify confusion on average (round up) vs maximum in the next bucket (casting) >> >> Instead of: >> Core: 3 4 5 >> Counter Freq: 2100 2100 2100 (MHz) >> 001 (us): 14880514 14880447 14880442 >> 002 (us): 0 0 0 >> 003 (us): 0 0 0 >> 004 (us): 0 0 0 >> 005 (us): 0 0 0 (including overflows) >> Minimum: 0 0 0 (us) >> Average: 1.000 1.000 1.000 (us) >> Maximum: 0 0 0 (us) >> Max-Min: 0 0 0 (us) >> >> We'd see: >> Core: 3 4 5 >> Counter Freq: 2100 2100 2100 (MHz) >> 001 (us): 12578842 12491108 12578752 >> 002 (us): 0 0 0 >> 003 (us): 0 0 0 >> 004 (us): 0 0 0 >> 005 (us): 0 0 0 (including overflows) >> Minimum: 0.033 0.035 0.035 (us) >> Average: 1.000 1.000 1.000 (us) >> Maximum: 0.129 0.153 0.134 (us) >> Max-Min: 0.095 0.118 0.099 (us) > > so core 3 has min 33ns and max 129ns while 1us on average? Yes, because avg rounds up. There are some other potential fixes coming like: - stop rounding up avg - splitting bucket 001 (us) which is bigger (0 - 1.99999) - adding the max bucket to the end (do not limit to 32us) ... but these are out of scope for this change. Folco > > Sebastian >