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Mon, 30 Oct 2023 14:26:51 -0400 (EDT) Message-ID: Date: Mon, 30 Oct 2023 14:27:10 -0400 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [POC][RFC][PATCH v2] sched: Extended Scheduler Time Slice Content-Language: en-US To: Steven Rostedt Cc: Linus Torvalds , Peter Zijlstra , LKML , Thomas Gleixner , Ankur Arora , linux-mm@kvack.org, x86@kernel.org, akpm@linux-foundation.org, luto@kernel.org, bp@alien8.de, dave.hansen@linux.intel.com, hpa@zytor.com, mingo@redhat.com, juri.lelli@redhat.com, vincent.guittot@linaro.org, willy@infradead.org, mgorman@suse.de, jon.grimm@amd.com, bharata@amd.com, raghavendra.kt@amd.com, boris.ostrovsky@oracle.com, konrad.wilk@oracle.com, jgross@suse.com, andrew.cooper3@citrix.com, Joel Fernandes , Youssef Esmat , Vineeth Pillai , Suleiman Souhlal , Ingo Molnar , Daniel Bristot de Oliveira References: <20231025235413.597287e1@gandalf.local.home> <20231026105944.GJ33965@noisy.programming.kicks-ass.net> <20231026071413.4ed47b0e@gandalf.local.home> <7871472b-a0c4-4475-9671-69a3244f956d@efficios.com> <20231026164549.14d45c60@gandalf.local.home> <644da047-2f7a-4d55-a339-f2dc28d2c852@efficios.com> <20231027122442.5c76dd62@gandalf.local.home> <20231027124930.3753cdd4@gandalf.local.home> <20231030094508.031357b4@gandalf.local.home> <20231030141956.05661b90@gandalf.local.home> From: Mathieu Desnoyers In-Reply-To: <20231030141956.05661b90@gandalf.local.home> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: BCB56120009 X-Stat-Signature: 9gdqokcsiarjdkmmfyjdemt9kk59heau X-HE-Tag: 1698690412-285118 X-HE-Meta: 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 DcWDrJxv WzWN3cFZgI1XYLq9UdNKQ1CkbCVOgmjis/d5IK3KnIyKdhdo8a6ocq0yK/gkRR6+KIbz9CVrjtgtDGtGyx5crQuJ/9amHj4MmOETTx20R5Rrl709leFuk5HaNSPC9pVJNzIM+1F3U1ETK9VtlLGUFwkORxj+hWeTYryj1B9o/KQoQobFgPwcru/vNZ8OX7r/A1NGLbZ4EIyF5QhXgiO8IsMNIv9L9w2xuRZ5ZwEJPr6D3gHx7TBnPugqoEvTQLrQVC+aVJgdvL5ywxA304wrLhiFLDPZL/NbKibCA3KYXFmpmR5taDH66md1ILq6w/lVxGKv+ X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 2023-10-30 14:19, Steven Rostedt wrote: > On Mon, 30 Oct 2023 14:05:05 -0400 > Mathieu Desnoyers wrote: > >> If you have the nesting counter, why do you need the explicit on/off >> switch ? > > Because I gave up when I found that one of the lwlocks seemed to take a long > time (pretty much the entire test) or I couldn't find how it was unlocked > (the code isn't trivial). > > So I just made every unlock disable the extended time slot. I need to go > back and enable both a counter and an on/off as I now realize that the spin > locks (called within the lwlock) will disable the extend time before the > lwlock is released. This should work if I have the spinlocks inc and dec > (they are straight forward and all locks are associated with an easily > found unlock), and have the lwlock use bit 31 as an on/off switch. This extra on/off switch appears to be working around userspace issues. > Anyway, I would let user space decide what it wants to do, and giving it 31 > bits to say "I'm extended" and let user space come up with how it handles > those 31 bits. If this makes it into the RSEQ uapi, RSEQ should state how userspace should collaborate wrt those bits (e.g. nesting counter protocol), even though it's not a kernel ABI per se. Otherwise we'll just push this to libc to specify this, which is odd. Thanks, Mathieu -- Mathieu Desnoyers EfficiOS Inc. https://www.efficios.com