Messages in this thread | | | Date | Tue, 16 Apr 2024 15:44:29 -0500 | Subject | Re: [PATCH v1 02/31] x86/resctrl: Add a helper to avoid reaching into the arch code resource list | From | "Moger, Babu" <> |
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Hi Dave,
On 4/16/24 11:15, Dave Martin wrote: > On Mon, Apr 15, 2024 at 03:28:18PM -0500, Moger, Babu wrote: >> Hi James/Dave, >> >> On 3/21/24 11:50, James Morse wrote: >>> Resctrl occasionally wants to know something about a specific resource, >>> in these cases it reaches into the arch code's rdt_resources_all[] >>> array. >>> >>> Once the filesystem parts of resctrl are moved to /fs/, this means it >>> will need visibility of the architecture specific struct >>> resctrl_hw_resource definition, and the array of all resources. >>> All architectures would also need a r_resctrl member in this struct. >>> >>> Instead, abstract this via a helper to allow architectures to do >>> different things here. Move the level enum to the resctrl header and >>> add a helper to retrieve the struct rdt_resource by 'rid'. >>> >>> resctrl_arch_get_resource() should not return NULL for any value in >>> the enum, it may instead return a dummy resource that is >>> !alloc_enabled && !mon_enabled. >> >> Nit. >> You may want to drop the second half of the statement. We don't have a >> dummy resource. > > I guess not, but MPAM will, although I haven't fully understood the > logic. See: > > https://git.kernel.org/pub/scm/linux/kernel/git/morse/linux.git/tree/drivers/platform/mpam/mpam_resctrl.c?h=mpam/snapshot/v6.7-rc2 > > (Search for "dummy".) > > > In any case, the statement above is part of the definition of the new > interface: the resctrl core code is going to explicitly need to cope > with a dummy resource being returned, and the arch code is required > to return a pointer to something and not NULL. > > So I would say that it is appropriate (or, at the very least, harmless) > to keep that statement here?
Ok. fine. > >> >>> >>> Signed-off-by: James Morse <james.morse@arm.com> >>> --- >>> arch/x86/kernel/cpu/resctrl/core.c | 10 +++++++++- >>> arch/x86/kernel/cpu/resctrl/ctrlmondata.c | 2 +- >>> arch/x86/kernel/cpu/resctrl/internal.h | 10 ---------- >>> arch/x86/kernel/cpu/resctrl/monitor.c | 8 ++++---- >>> arch/x86/kernel/cpu/resctrl/rdtgroup.c | 15 +++++++-------- >>> include/linux/resctrl.h | 17 +++++++++++++++++ >>> 6 files changed, 38 insertions(+), 24 deletions(-) >>> > > [...] > >>> diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c >>> index 1767c1affa60..45372b6a6215 100644 >>> --- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c >>> +++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c > > [...] > >>> @@ -2625,10 +2625,10 @@ static void schemata_list_destroy(void) >>> >>> static int rdt_get_tree(struct fs_context *fc) >>> { >>> + struct rdt_resource *l3 = resctrl_arch_get_resource(RDT_RESOURCE_L3); >> >> Its is probably best to keep the resource name as r here to be consistent >> with other changes. >> >>> struct rdt_fs_context *ctx = rdt_fc2context(fc); >>> unsigned long flags = RFTYPE_CTRL_BASE; >>> struct rdt_domain *dom; >>> - struct rdt_resource *r; >>> int ret; >>> >>> cpus_read_lock(); >>> @@ -2701,8 +2701,7 @@ static int rdt_get_tree(struct fs_context *fc) >>> resctrl_mounted = true; >>> >>> if (is_mbm_enabled()) { >>> - r = &rdt_resources_all[RDT_RESOURCE_L3].r_resctrl; >>> - list_for_each_entry(dom, &r->domains, list) >>> + list_for_each_entry(dom, &l3->domains, list) >>> mbm_setup_overflow_handler(dom, MBM_OVERFLOW_INTERVAL, >>> RESCTRL_PICK_ANY_CPU); >>> } >>> @@ -3878,7 +3877,7 @@ static int rdtgroup_show_options(struct seq_file *seq, struct kernfs_root *kf) > > [...] > >> Thanks >> Babu Moger > > [...] > > Yes, this does look a bit odd. > > This looks like a no-op change to me -- I think that > resctrl_arch_get_resource() is supposed to be without side-effects, > so I would have expected this to be a one-line change at the assignment > to r, with no particular need for renaming r. > > Does that make sense to you, or is there some complexity I'm not > noticing here?
No other complexity.. Just keep the variable name as r.
struct rdt_resource *r = resctrl_arch_get_resource(RDT_RESOURCE_L3);
-- Thanks Babu Moger
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