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Message-ID: <87v8a6fnhg.fsf@yhuang6-desk2.ccr.corp.intel.com> Date: Mon, 13 Nov 2023 09:31:07 +0800 From: "Huang, Ying" <ying.huang@...el.com> To: Gregory Price <gregory.price@...verge.com> Cc: Gregory Price <gourry.memverge@...il.com>, <linux-kernel@...r.kernel.org>, <linux-cxl@...r.kernel.org>, <linux-mm@...ck.org>, <cgroups@...r.kernel.org>, <linux-doc@...r.kernel.org>, <akpm@...ux-foundation.org>, <mhocko@...nel.org>, <tj@...nel.org>, <lizefan.x@...edance.com>, <hannes@...xchg.org>, <corbet@....net>, <roman.gushchin@...ux.dev>, <shakeelb@...gle.com>, <muchun.song@...ux.dev> Subject: Re: [RFC PATCH v4 0/3] memcg weighted interleave mempolicy control Gregory Price <gregory.price@...verge.com> writes: > On Fri, Nov 10, 2023 at 02:16:05PM +0800, Huang, Ying wrote: >> Gregory Price <gourry.memverge@...il.com> writes: >> >> > This patchset implements weighted interleave and adds a new cgroup >> > sysfs entry: cgroup/memory.interleave_weights (excluded from root). >> > >> > The il_weight of a node is used by mempolicy to implement weighted >> > interleave when `numactl --interleave=...` is invoked. By default >> > il_weight for a node is always 1, which preserves the default round >> > robin interleave behavior. >> >> IIUC, this makes it almost impossible to set the default weight of a >> node from the node memory bandwidth information. This will make the >> life of users a little harder. >> >> If so, how about use a new memory policy mode, for example >> MPOL_WEIGHTED_INTERLEAVE, etc. >> > > weights are also inherited from parent cgroups, so if you set them in > parent slices you can automatically set update system settings. > > by default the parent slice weights will always be 1 until set > otherwise. Once they're set, children inherit naturally. > > Maybe there's an argument here for including interleave_weights in the > root cgroup. Even if the interleave_weights is introduced in root cgroup, the initial default weight need to be 1 to be back-compatible with the original MPOL_INTERLEAVE. If we don't reuse MPOL_INTERLEAVE, but use a new memory policy mode (say MPOL_WEIGHTED_INTERLEAVE). The default values of the interleave weight in root cgroup needn't to be 1. So, we can provide a more helpful default interleave weight based on the node memory bandwidth information (e.g., from HMAT, CDAT, etc). That will make users life much easier. Do you agree? -- Best Regards, Huang, Ying
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