Messages in this thread Patch in this message | | | Subject | Re: [RFC PATCH 01/10] perf workqueue: threadpool creation and destruction | From | Riccardo Mancini <> | Date | Thu, 15 Jul 2021 18:31:07 +0200 |
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Hi Arnaldo,
thanks for reviewing the patch!
On Wed, 2021-07-14 at 11:16 -0300, Arnaldo Carvalho de Melo wrote: <SNIP> > > + > > +enum threadpool_status { > > + THREADPOOL_STATUS__STOPPED, /* no threads */ > > + THREADPOOL_STATUS__ERROR, /* errors */ > > + THREADPOOL_STATUS__MAX > > +}; > > + > > +struct threadpool_struct { > > Can this be just 'struct threadpool'? I think its descriptive enough:
I agree, but I wanted to keep the naming consistent between workqueue.c and threadpool.c.
> > > + int nr_threads; /* number of threads in the > > pool */ > > + struct thread_struct *threads; /* array of threads in the > > pool */ > > + struct task_struct *current_task; /* current executing > > function > > */ > > + enum threadpool_status status; /* current status of the > > pool > > */ > > +}; > > + > > +struct thread_struct { > > + int idx; /* idx of thread in pool- > > > threads */ > > + pid_t tid; /* tid of thread */ > > + struct threadpool_struct *pool; /* parent threadpool */ > > + struct { > > + int from[2]; /* messages from thread > > (acks) > > */ > > + int to[2]; /* messages to thread > > (commands) */ > > + } pipes; > > +}; > > This one, since we have already a 'struct thread' in tools/perf, to > represent a PERF_RECORD_FORK, perhaps we can call it 'struct > threadpool_entry'?
Agreed.
> > > + > > +/** > > + * init_pipes - initialize all pipes of @thread > > + */ > > +static void init_pipes(struct thread_struct *thread) > > +{ > > + thread->pipes.from[0] = -1; > > + thread->pipes.from[1] = -1; > > + thread->pipes.to[0] = -1; > > + thread->pipes.to[1] = -1; > > +} > > + > > +/** > > + * open_pipes - open all pipes of @thread > > + */ > > +static int open_pipes(struct thread_struct *thread) > > Here please: > > threadpool_entry__open_pipes() > > Its longer, but helps with ctags/cscope navigation and we can go > directly to it via: > > :ta threadpool_entry__open_p<TAB> > > While 'ta: open_pipes' may bo to various places where this idiom is > used.
Agreed.
<SNIP> > > +/** > > + * create_threadpool - create a fixed threadpool with @n_threads threads > > + */ > > +struct threadpool_struct *create_threadpool(int n_threads) > > > Is this already something the kernel has and thus we should keep the > naming? I couldn't find it in the kernel, so please name it: > > struct threadpool *threadpool__new(int nthreads)
As before, I did this to keep consistency with workqueue. Since this threadpool+workqueue can be a standalone library, I preferred to keep the naming consistent inside it, instead of making it consistent with perf (this is what I was referring to in the cover letter, not just the workqueue API). What do you think? I also prefer perf's naming conventions, but it'd feel strange to use two different naming conventions inside the same library.
> > > +{ > > + int ret, t; > > + struct threadpool_struct *pool = malloc(sizeof(*pool)); > > + > > + if (!pool) { > > + pr_err("threadpool: cannot allocate pool: %s\n", > > + strerror(errno));o > > Humm, pr_err() at this level isn't appropriate, please make callers > complain.
ok.
> > > + return NULL; > > + } > > + > > + if (n_threads <= 0) { > > + pr_err("threadpool: invalid number of threads: %d\n", > > + n_threads); > > pr_debug()
ok
> > > + goto out_free_pool; > > + } > > + > > + pool->nr_threads = n_threads; > > + pool->current_task = NULL; > > + > > + pool->threads = malloc(n_threads * sizeof(*pool->threads)); > > + if (!pool->threads) { > > + pr_err("threadpool: cannot allocate threads: %s\n", > > + strerror(errno)); > > + goto out_free_pool; > > + } > > + > > + for (t = 0; t < n_threads; t++) { > > + pool->threads[t].idx = t; > > + pool->threads[t].tid = -1; > > + pool->threads[t].pool = pool; > > + init_pipes(&pool->threads[t]); > > + } > > + > > + for (t = 0; t < n_threads; t++) { > > + ret = open_pipes(&pool->threads[t]); > > + if (ret) > > + goto out_close_pipes; > > + } > > + > > + pool->status = THREADPOOL_STATUS__STOPPED; > > + > > + return pool; > > + > > +out_close_pipes: > > + for (t = 0; t < n_threads; t++) > > + close_pipes(&pool->threads[t]); > > + > > + free(pool->threads); > > +out_free_pool: > > + free(pool); > > + return NULL; > > Here we can use ERR_PTR()/PTR_ERR() to let the caller know what was the > problem, i.e. we can ditch all the pr_err/pr_debug(), etc and instead > have a threadpool__strerror(struct threadpool *pool, int err) like we > have for 'struct evsel', please take a look at evsel__open_strerror().
Thanks, I'll have a look at it. So, what I sould do is not use pr_* higher than debug inside library code and return meaningful errors through PR_ERR, right?
> > > > +} > > + > > +/** > > + * destroy_threadpool - free the @pool and all its resources > > + */ > > +void destroy_threadpool(struct threadpool_struct *pool) > > > void threadpool__delete(struct threadpool *pool) > > +{ > > + int t; > > + > > + if (!pool) > > + return; > > + > > + WARN_ON(pool->status != THREADPOOL_STATUS__STOPPED > > + && pool->status != THREADPOOL_STATUS__ERROR); > > + > > + for (t = 0; t < pool->nr_threads; t++) > > + close_pipes(&pool->threads[t]); > > reset pool->threads[t] to -1
already inside close_pipes. I agree it might be confusing without the threadpool_entry__ prefix.
> > > + > > + free(pool->threads); > > zfree
In general, when should I use zfree instead of free?
> > > + free(pool); > > +} > > + > > +/** > > + * threadpool_size - get number of threads in the threadpool > > + */ > > +int threadpool_size(struct threadpool_struct *pool) > > threadpool__size()
ok
Thanks, Riccardo
> > > +{ > > + return pool->nr_threads; > > +} > > diff --git a/tools/perf/util/workqueue/threadpool.h > > b/tools/perf/util/workqueue/threadpool.h > > new file mode 100644 > > index 0000000000000000..2b9388c768a0b588 > > --- /dev/null > > +++ b/tools/perf/util/workqueue/threadpool.h > > @@ -0,0 +1,19 @@ > > +/* SPDX-License-Identifier: GPL-2.0 */ > > +#ifndef __WORKQUEUE_THREADPOOL_H > > +#define __WORKQUEUE_THREADPOOL_H > > + > > +struct threadpool_struct; > > +struct task_struct; > > + > > +typedef void (*task_func_t)(int tidx, struct task_struct *task); > > + > > +struct task_struct { > > + task_func_t fn; > > +}; > > + > > +extern struct threadpool_struct *create_threadpool(int n_threads); > > +extern void destroy_threadpool(struct threadpool_struct *pool); > > + > > +extern int threadpool_size(struct threadpool_struct *pool); > > + > > +#endif /* __WORKQUEUE_THREADPOOL_H */ > > -- > > 2.31.1 >
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