Messages in this thread | | | Date | Thu, 15 Jul 2021 17:48:20 -0300 | From | Arnaldo Carvalho de Melo <> | Subject | Re: [RFC PATCH 01/10] perf workqueue: threadpool creation and destruction |
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Em Thu, Jul 15, 2021 at 06:31:07PM +0200, Riccardo Mancini escreveu: > 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.
See my comment on the other message about this naming dilemma :-)
> > > > > +{ > > > + 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?
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 > > > > > > > >
--
- Arnaldo
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