Messages in this thread | | | From | Rusty Russell <> | Subject | Re: [PATCH] modules: Use a better scheme for refcounting | Date | Fri, 16 May 2008 10:09:11 +1000 |
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On Friday 16 May 2008 06:40:37 Eric Dumazet wrote: > Current refcounting for modules (done if CONFIG_MODULE_UNLOAD=y) > is using a lot of memory.
Hi Eric,
I like this patch! The plan was always to create a proper dynamic per-cpu allocator which used the normal per-cpu offsets, but I think module refcounts are worthwhile as a special case.
Any chance I can ask you look at the issue of full dynamic per-cpu allocation? The problem of allocating memory which is laid out precisely as the original per-cpu alloc is vexing on NUMA, and probably requires reserving virtual address space and remapping into it, but the rewards would be maximally-efficient per-cpu accessors, and getting rid of that boutique allocator in module.c.
Only minor commentry on the patch itself:
> +#ifdef CONFIG_SMP > + char *refptr; > +#else
void * would seem more natural here (love those gcc'isms)
> +#if defined(CONFIG_MODULE_UNLOAD) && defined(CONFIG_SMP) > + void *refptr = NULL; > +#endif
Looks like you can skip this if you assign to mod->refptr directly below:
> +#if defined(CONFIG_MODULE_UNLOAD) && defined(CONFIG_SMP) > + refptr = percpu_modalloc(sizeof(local_t), sizeof(local_t), mod->name); > + if (!refptr) > + goto free_mod; > + mod->refptr = refptr; > +#endif
And finally:
> +#if defined(CONFIG_MODULE_UNLOAD) && defined(CONFIG_SMP) > + if (refptr) > + percpu_modfree(refptr); > +#endif
This if (refptr) seems redundant.
Thanks! Rusty.
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