On Mon, 16 Oct 2023 00:06:11 +0800 "wuqiang.matt" <[email protected]> wrote:
> On 2023/10/15 23:43, Masami Hiramatsu (Google) wrote: > > On Sun, 15 Oct 2023 13:32:47 +0800 > > "wuqiang.matt" <[email protected]> wrote: > > > >> objpool is a scalable implementation of high performance queue for > >> object allocation and reclamation, such as kretprobe instances. > >> > >> With leveraging percpu ring-array to mitigate hot spots of memory > >> contention, it delivers near-linear scalability for high parallel > >> scenarios. The objpool is best suited for the following cases: > >> 1) Memory allocation or reclamation are prohibited or too expensive > >> 2) Consumers are of different priorities, such as irqs and threads > >> > >> Limitations: > >> 1) Maximum objects (capacity) is fixed after objpool creation > >> 2) All pre-allocated objects are managed in percpu ring array, > >> which consumes more memory than linked lists > >> > > > > Thanks for updating! This looks good to me except 2 points. > > > > [...] > >> + > >> +/* initialize object pool and pre-allocate objects */ > >> +int objpool_init(struct objpool_head *pool, int nr_objs, int object_size, > >> + gfp_t gfp, void *context, objpool_init_obj_cb objinit, > >> + objpool_fini_cb release) > >> +{ > >> + int rc, capacity, slot_size; > >> + > >> + /* check input parameters */ > >> + if (nr_objs <= 0 || nr_objs > OBJPOOL_NR_OBJECT_MAX || > >> + object_size <= 0 || object_size > OBJPOOL_OBJECT_SIZE_MAX) > >> + return -EINVAL; > >> + > >> + /* align up to unsigned long size */ > >> + object_size = ALIGN(object_size, sizeof(long)); > >> + > >> + /* calculate capacity of percpu objpool_slot */ > >> + capacity = roundup_pow_of_two(nr_objs); > > > > This must be 'roundup_pow_of_two(nr_objs + 1)' because if nr_objs is power > > of 2 and all objects are pushed on the same slot, tail == head. This > > means empty and full is the same. > > That won't happen. Would tail and head wrap only when >= 2^32. When all > objects are pushed to the same slot, tail will be (head + capacity). Ah, indeed. OK. > > > > >> + if (!capacity) > >> + return -EINVAL; > >> + > >> + /* initialize objpool pool */ > >> + memset(pool, 0, sizeof(struct objpool_head)); > >> + pool->nr_cpus = nr_cpu_ids; > >> + pool->obj_size = object_size; > >> + pool->capacity = capacity; > >> + pool->gfp = gfp & ~__GFP_ZERO; > >> + pool->context = context; > >> + pool->release = release; > >> + slot_size = pool->nr_cpus * sizeof(struct objpool_slot); > >> + pool->cpu_slots = kzalloc(slot_size, pool->gfp); > >> + if (!pool->cpu_slots) > >> + return -ENOMEM; > >> + > >> + /* initialize per-cpu slots */ > >> + rc = objpool_init_percpu_slots(pool, nr_objs, context, objinit); > >> + if (rc) > >> + objpool_fini_percpu_slots(pool); > >> + else > >> + refcount_set(&pool->ref, pool->nr_objs + 1); > >> + > >> + return rc; > >> +} > >> +EXPORT_SYMBOL_GPL(objpool_init); > >> + > > > > [...] > > > >> + > >> +/* drop unused objects and defref objpool for releasing */ > >> +void objpool_fini(struct objpool_head *pool) > >> +{ > >> + void *obj; > >> + > >> + do { > >> + /* grab object from objpool and drop it */ > >> + obj = objpool_pop(pool); > >> + > >> + /* > >> + * drop reference of objpool anyway even if > >> + * the obj is NULL, since one extra ref upon > >> + * objpool was already grabbed during pool > >> + * initialization in objpool_init() > >> + */ > >> + if (refcount_dec_and_test(&pool->ref)) > >> + objpool_free(pool); > > > > Nit: you can call objpool_drop() instead of repeating the same thing here. > > objpool_drop won't deref objpool if given obj is NULL. But here we need > drop objpool anyway even if obj is NULL. I guess you decrement for the 'objpool' itself if obj=NULL, but I think it is a bit hacky (so you added the comment). e.g. rethook is doing something like below. --- /* extra count for this pool itself */ count = 1; /* make the pool empty */ while (objpool_pop(pool)) count++; if (refcount_sub_and_test(count, &pool->ref)) objpool_free(pool); --- > > > Thank you, > > > >> + } while (obj); > >> +} > >> +EXPORT_SYMBOL_GPL(objpool_fini); > >> -- > >> 2.40.1 > >> > > Thanks for you time > > -- Masami Hiramatsu (Google) <[email protected]>
