From: "Michal Koutný" <mkoutny@suse.com> To: Haifeng Xu <haifeng.xu@shopee.com> Cc: tj@kernel.org, lizefan.x@bytedance.com, hannes@cmpxchg.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] cgroup: Simplify code in css_set_move_task Date: Mon, 31 Oct 2022 14:11:40 +0100 [thread overview] Message-ID: <20221031131140.GC27841@blackbody.suse.cz> (raw) In-Reply-To: <adb7418c-39a2-6202-970a-a039ad8201dd@shopee.com> [-- Attachment #1: Type: text/plain, Size: 1111 bytes --] Hello. > 1) If calls 'css_set_update_populated' , the cset is either getting the > first task or losing the last. There is a need to update the populated > state of the cset only when 'css_set_populated' returns false. > In other words, the last has been deleted from from_cset and the first > hasn't been added to to_cset yet. I've likely misread the condition previously. I see how this works now (update happens after "from_cset" but before "to_cset" migration). > 3) In order to update the populated state of to_cset the same way > from_cset does, 'css_set_update_populated' is also invoked during the > process of moving a task to to_cset. As I think more about this in the context of vertical migrations (ancestor<->descendant, such as during controller dis- or enablement), I'm afraid the inverted order would lead to "spurious" emptiness notifications in ancestors (in the case a there is just a single task that migrates parent->child, parent/cgroup.populated would generate and event that'd be nullified by the subsequent population of the child). So I'm not sure the change is worth it. Michal [-- Attachment #2: Digital signature --] [-- Type: application/pgp-signature, Size: 228 bytes --]
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From: "Michal Koutný" <mkoutny-IBi9RG/b67k@public.gmane.org> To: Haifeng Xu <haifeng.xu-LL2PKPoSiP3QT0dZR+AlfA@public.gmane.org> Cc: tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org, lizefan.x-EC8Uxl6Npydl57MIdRCFDg@public.gmane.org, hannes-druUgvl0LCNAfugRpC6u6w@public.gmane.org, cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org Subject: Re: [PATCH] cgroup: Simplify code in css_set_move_task Date: Mon, 31 Oct 2022 14:11:40 +0100 [thread overview] Message-ID: <20221031131140.GC27841@blackbody.suse.cz> (raw) In-Reply-To: <adb7418c-39a2-6202-970a-a039ad8201dd-LL2PKPoSiP3QT0dZR+AlfA@public.gmane.org> [-- Attachment #1: Type: text/plain, Size: 1111 bytes --] Hello. > 1) If calls 'css_set_update_populated' , the cset is either getting the > first task or losing the last. There is a need to update the populated > state of the cset only when 'css_set_populated' returns false. > In other words, the last has been deleted from from_cset and the first > hasn't been added to to_cset yet. I've likely misread the condition previously. I see how this works now (update happens after "from_cset" but before "to_cset" migration). > 3) In order to update the populated state of to_cset the same way > from_cset does, 'css_set_update_populated' is also invoked during the > process of moving a task to to_cset. As I think more about this in the context of vertical migrations (ancestor<->descendant, such as during controller dis- or enablement), I'm afraid the inverted order would lead to "spurious" emptiness notifications in ancestors (in the case a there is just a single task that migrates parent->child, parent/cgroup.populated would generate and event that'd be nullified by the subsequent population of the child). So I'm not sure the change is worth it. Michal [-- Attachment #2: Digital signature --] [-- Type: application/pgp-signature, Size: 228 bytes --]
next prev parent reply other threads:[~2022-10-31 13:11 UTC|newest] Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top 2022-10-20 7:47 [PATCH] cgroup: Simplify code in css_set_move_task haifeng.xu 2022-10-20 7:47 ` haifeng.xu 2022-10-27 8:05 ` Michal Koutný 2022-10-27 8:05 ` Michal Koutný 2022-10-28 11:29 ` Haifeng Xu 2022-10-28 11:29 ` Haifeng Xu 2022-10-31 13:11 ` Michal Koutný [this message] 2022-10-31 13:11 ` Michal Koutný 2022-11-03 2:13 ` Haifeng Xu 2022-11-03 2:13 ` Haifeng Xu 2022-11-03 2:31 ` Tejun Heo 2022-11-03 2:31 ` Tejun Heo 2022-11-03 14:55 ` Haifeng Xu
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